Error While Decrypting the URL

I'm facing below error while decrypting the URL.

"System.StringException: Unrecognized base64 character: %"

Below is my Encryption & decryption code.

public static string encryption(String sURL){
        
        Boolean bContainsURL = sURL.contains('?');
        String sParam = bContainsURL ? sURL.subStringAfter('?') : sURL;
        sURL = bContainsURL ? sURL.subStringBefore('?') : '';
        encryptCustomSettings__c oEncryptionKeys = encryptCustomSettings__c.getValues('EncryptionKey');
        Blob bbIvKey = blob.valueOf(oEncryptionKeys.IV_Key__c);
        blob bbPrivateKey = Crypto.generateDigest('SHA256', blob.valueOf(oEncryptionKeys.Private_Key__c));
        
        blob bbEncryptedParam=Crypto.encrypt('AES256', bbPrivateKey,bbIvKey,  blob.valueOf(sParam));
        return sURL+'?key='+EncodingUtil.URLencode(EncodingUtil.base64Encode(bbEncryptedParam),'UTF-8');
    }

encryption is getting successfull & getting encrypted link as "{URL}key=XiP3ucdyVii7vxwWOv67iA3PNHpvOlEdkFdFzsSIXus%9D"

but while passing the same value to decrypt getting the error message.

Decryption code

public static string decryption(String sURL){
        
        String sDecryptedURL;
        if(String.isNotBlank(sURL)){
  
            encryptCustomSettings__c oEncryptionKeys = encryptCustomSettings__c.getValues('EncryptionKey');
            Blob bbIvKey = blob.valueOf(oEncryptionKeys.IV_Key__c);
            blob bbPrivateKey = Crypto.generateDigest('SHA256', blob.valueOf(oEncryptionKeys.Private_Key__c));
            
            Blob bbDecoded = EncodingUtil.base64Decode(sURL);
            Blob bbDecrypted = Crypto.decrypt('AES256', bbPrivateKey, bbIvKey,  bbDecoded);
            sDecryptedURL = bbDecrypted.toString();
            
        }
        return sDecryptedURL;
    }