[SalesForce] problem adding custom button to list view

I want to add a custom button to the list view of Contacts but it is not working. I go to Object Manager… Contacts… Search Layouts… List View… Edit… Custom Buttons… add my button to the list of Selected Buttons. When I go back to Contacts, it does not appear. If I remove Standard Buttons by unchecking them, nothing changes. Any direction would be appreciated.

I'm using Lightning.

public class createNewContactController_ext {
//variables for the student
private final Contact con;
private ApexPages.StandardController stdController;
String StudentRecordType = '0121H000001If0DQAS';


//variables for dependent spouse
public List<Contact> spsList {get;set;} //using list so that I don't have to declare each variable
public Integer rowNumsps{get;set;}
String DepedendentRecordType = '0121H000001If0IQAS';


//variables for dependent children
public List<Contact> depList {get;set;}
public Integer rowNum{get;set;}

//initialize 
public createNewContactController_ext(ApexPages.StandardController stdController) {
    this.con = (Contact)stdController.getRecord();
    depList = new List<Contact>();  
    spsList = new List<Contact>();
}
    //for inserting additional rows in dependent spouse table
public void insertRowsps(){
    spsList.add(new Contact(recordTypeID=DepedendentRecordType)); 
}

    //for deleting rows from dependent spouse table
public void delRowsps(){
    rowNum = Integer.valueOf(apexpages.currentpage().getparameters().get('indexsps'));
    depList.remove(rowNumsps);   
}

//for inserting additional rows in dependent children table
public void insertRow(){
    depList.add(new Contact(recordTypeID=DepedendentRecordType)); 
}


//for deleting rows from dependent children table
public void delRow(){
    rowNum = Integer.valueOf(apexpages.currentpage().getparameters().get('index'));
    depList.remove(rowNum);   
}

//save the records
public PageReference save(){

    //save the student
    insert con;

    //save the spouse
    insert spsList;
    for (Contact sps : spsList){
        hed__Relationship__c spsrel = new   hed__Relationship__c(hed__Contact__c=con.Id, hed__RelatedContact__c=sps.Id, hed__Type__c='Spouse');
      insert spsrel;
    }

    //save the child dependents
    insert depList;
    for (Contact dep : depList){
      hed__Relationship__c rel = new    hed__Relationship__c(hed__Contact__c=con.Id, hed__RelatedContact__c=dep.Id, hed__Type__c='Child');
      insert rel;
    }    

    //redirect to the detail page of the student
    PageReference redirectPage = new ApexPages.StandardController(con).view();
    redirectPage.setRedirect(true);
    redirectPage.getParameters().put('id',con.Id);
    return redirectPage;
    }

}

the vf page:

    <apex:page standardController="Contact" extensions="createNewContactController_ext" docType="html-5.0" >
<apex:pageBlock title="Student">
    <apex:form >
        <apex:pageBlockSection >       
            <apex:inputField value="{!Contact.FirstName}" />
            <apex:inputField value="{!Contact.LastName}" />
            <apex:inputField value="{!Contact.Email}" required="true" />
            <apex:inputField value="{!Contact.Birthdate}" showDatePicker="true"/>
            <apex:inputField value="{!Contact.Affiliated_Community__c}" />
            <apex:inputField value="{!Contact.Beneficiary_Number__c}" />
            <apex:inputField value="{!Contact.Birth_Place__c}" />
            <apex:inputField value="{!Contact.Social_Insurance_Number__c}" />
            <apex:inputField value="{!Contact.hed__Gender__c}" />
            <apex:inputField value="{!Contact.Counselor__c}" />
            <apex:inputField value="{!Contact.Permanent_Code__c}" />
            <apex:inputField value="{!Contact.Facebook_Profile__c}" />
            <apex:inputField value="{!Contact.Language_Preference__c}" />
        </apex:pageBlockSection>
        <apex:pageBlockSection title="Student Permanent Address">
            <apex:inputField value="{!Contact.MailingStreet}" />
            <apex:inputField value="{!Contact.MailingCity}" />
            <apex:inputField value="{!Contact.MailingState}" /> 
            <apex:inputField value="{!Contact.MailingPostalCode}" label="Province" />
            <apex:inputField value="{!Contact.MailingCity}" />
            <apex:inputField value="{!Contact.MailingState}" />        
        </apex:pageBlockSection> 
        <apex:pageBlock title="Dependent Spouse" >
            <apex:variable var="rowNumsps" value="{!0}"  />  
            <apex:pageBlockTable value="{!spsList}" var="spstable">
                <apex:facet name="footer">
                    <apex:commandLink value="Add" action="{!insertRowsps}"/>
                </apex:facet>
                <apex:column headerValue="First Name">
                    <apex:inputField value="{!spstable.FirstName}"/>
                </apex:column>
                <apex:column headerValue="Last Name">
                    <apex:inputText value="{!spstable.LastName}"/>
                </apex:column>   
                <apex:column headerValue="Birthdate">
                    <apex:inputField value="{!spstable.Birthdate}"/>
                </apex:column>   
                <apex:column headerValue="Beneficiary Number">
                    <apex:inputField value="{!spstable.Beneficiary_Number__c}"/>
                </apex:column>   
                <apex:column headerValue="Social Insurance Number">
                    <apex:inputField value="{!spstable.Social_Insurance_Number__c}"/>
                </apex:column>
                <apex:column headerValue="Delete" >
                    <apex:commandLink style="font-size:15px; font-weight:bold; text-align:center;color:red;" value="X" action="{!delRow}">
                        <apex:param value="{!rowNumsps}" name="indexsps" />
                    </apex:commandLink>
                    <apex:variable var="rowNumsps" value="{!rowNumsps+1}"/>
                </apex:column>
            </apex:pageBlockTable>
        </apex:pageBlock>
        <apex:variable var="rowNum" value="{!0}"  />
        <apex:pageBlock title="Dependent Children" >
            <apex:variable var="rowNum" value="{!0}"  />  
            <apex:pageBlockTable value="{!depList}" var="deptable">
                <apex:facet name="footer">
                    <apex:commandLink value="Add" action="{!insertRow}"/>
                </apex:facet>
                <apex:column headerValue="First Name">
                    <apex:inputField value="{!deptable.FirstName}"/>
                </apex:column>
                <apex:column headerValue="Last Name">
                    <apex:inputText value="{!deptable.LastName}"/>
                </apex:column>   
                <apex:column headerValue="Birthdate">
                    <apex:inputField value="{!deptable.Birthdate}"/>
                </apex:column>   
                <apex:column headerValue="Beneficiary Number">
                    <apex:inputField value="{!deptable.Beneficiary_Number__c}"/>
                </apex:column>   
                <apex:column headerValue="Social Insurance Number">
                    <apex:inputField value="{!deptable.Social_Insurance_Number__c}"/>
                </apex:column>         
                <apex:column headerValue="Delete" >
                    <apex:commandLink style="font-size:15px; font-weight:bold; text-align:center;color:red;" value="X" action="{!delRow}">
                        <apex:param value="{!rowNum}" name="index" />
                    </apex:commandLink>
                    <apex:variable var="rowNum" value="{!rowNum+1}"/>
                </apex:column>          
            </apex:pageBlockTable>
        </apex:pageBlock>
        <apex:commandButton value="save" action="{!save}" />  
    </apex:form>    
</apex:pageBlock>
</apex:page>