It seems that recent events might have had a part in the cause of this issue.
Basically this happens because game updates on steam take precedence over workshop content when it comes to downloads, and sadly by default steam is set to not download updates while a game is being played.
Which leads to the workshop content not being downloaded because it has to wait for the game updates that aren’t being downloaded.
luckily there’s a fix to this:
Head into the steam settings under the downloads section, then click on the “allow downloads during gameplay” box so that steam is able to finish queued downloads while you’re playing a game.
Then head into the tower unite properties in the library and go into updates, then make sure that the background downloads settings is set to either “follow my global settings” (only works if the global settings allows downloads while playing) or “always allow background downloads”.
Personally i recommend the “always allow background downloads” option because then you’re guaranteed that it will download while the game is playing.
Then you can easily boot up tower unite and play, all you need to do now is to be patient while steam downloads any queued updates, then when those are done it will move on to the workshop content and then the models should show in game and in the in game workshop window.