The host you use seems to be having difficulties, all assets load eternally.

Download this. It was recently updated with mod author features.
https://www.nexusmods.com/tabletopsimulator/mods/263?tab=files

You right click a workshop/save file, and do 'check for invalid links'. You can then right click a green invalid link (green means you have the file) and select 'Upload this asset to SteamCloud and replace URL'.

Then after that all you need to do is start up the game and upload the modified file to the workshop.