How to pin bodies using the Magneto-stick in TTT

Posting this question/answer here, since the solution doesn't appear to exist anywhere else (outside of my own steam forums post):

Apparently Garry's Mod uses Internet Explorer somehow for its "FastDL" downloading. If Internet Explorer can't connect to the internet for whatever reason, then Garry's Mod won't download anything.

In my case, IE was set to offline-mode. Setting it to online fixed the issue.

Other things you can try:

• Make sure Options --> Multiplayer --> Download Custom Content is set to Allow All Custom Files From Server

• Try adding the following lines to the bottom of your garry's mod config file, located at Steam\steamapps\<username>\garrysmod\garrysmod\cfg\config.cfg:

  cl_allowdownload 1
  cl_downloadfilter all
  download_debug 0
  sv_downloadurl ""
  

• Verify the integrity of the game files. Within Steam: Library --> Garry's Mod --> Right Click --> Properties --> Local Files --> "Verify Integrity of Game Cache"

• Try disabling your firewall/antivirus, or possibly other non-essential programs/services running.

• Try deleting your maps, lua, addons, and cache folders in the garrysmod folder, located at Steam\steamapps\<username>\garrysmod\garrysmod. Then verify your cache again.

• As a last resort, uninstall Garry's Mod completely and delete the garrysmod folder (which you'll have to do by hand, because there will be leftover files), then reinstall.

Are you running the server on a local machine at your place? In that case, try using internal LAN address to connect to it. If that still fails, the issue is with your computer's firewall, possibly. Try disabling it momentarily and connect to the server again. If that also fails, then the problem is most likely with SteamCMD. Check that you haven't accidentally changed the ports it's supposed to use.

If your server is on a computer with Gmod installed, try connecting to 127.0.0.1. This is the notorious loopback address, and makes the computer connect to itself. If that fails, then the problem is with SteamCMD. Like mentioned above, check that you haven't accidentally changed the ports it's supposed to use.

If all else fails, try using the HLDSUpdateTool instead. Although aging, and about to be phased out, it is still a viable alternative.