When I try to edit my game, I'm presented with a loading screen that never ends. Help?

Are you using quest online/web or offline/desktop ???

don't worry about this issue, it's very common as the reason why it doesn't load up is because something is messed up in the game code, the usual culprit is often an infinite/endless loop (but this usually doesn't interfere with loading up quest game and/as it crashes quest too)... so, probably it's some other code mess up (for example, maybe you accidentally deleted a part of code that's need for it to load up).

if you're using quest offline/desktop, then just right click on your game file on your computer (xxx.aslx) and open it with a text editor software (notepad, wordpad, apple: text editor, notepad++, etc), highlight all of it (this is your entire game code), copy it, and then paste it here, so we can scour through it looking for the code errors, and fixing them up for you.

if you're using quest online/web, then if you can, you'll need to download your game, and then do the above steps for the 'offline/desktop'.

if you can't download your game, you're going to need to get in contact with the new website/server owner, which I think is Manowar (but not sure), or if not him/her, someone will know who it is and help you get in contact with them.

here's a default/new game's code (so, if you're missing some in your code from this, that might be the culprit of why it's not loading up):

<asl version="550">

  <include ref="English.aslx" />
  <include ref="Core.aslx" />

  <game name="whatever_you_named_your_game_as">

    <attr name="gameid" type="string">some_randomly_generated_hash_string</attr>
    <attr name="version" type="string">1.0</attr>
    <attr name="firstpublished" type="string">2017</attr>

  </game>

  <object name="room">

    <inherit name="editor_room" />

    <object name="player">

      <inherit name="editor_object" />
      <inherit name="editor_player" />

    </object>

  </object>

</asl>