[2020] My mods refuse to download

That sounds like a Steam problem really.

As a test, Can you install th egame on a different computer and see if the problem happens there too?  

I was thinking you might have access to a machine from a friend or relative, just for this test.

But let's also try the HOI4 mod fix:

- unsubscribe from all mods
- delete the folder Documents/paradox/Stellaris/mod/
- delete the file Documents/paradox/Stellaris/mods_registry.json
- delete the file Documents/paradox/Stellaris/launcher-v2.sqlite
- subscribe to a few mods
- run the game up and see if those mods are now available to you.

I hope that does it for you!