1) Launch Hoi4 without any mods
2) Verify your vanilla checksum. Checksums for each version of the game are found here: https://hoi4.paradoxwikis.com/Patches#Version_history
3) If your vanilla checksum is not correct there are two options:
- Verify game files
- Full uninstall
4) If your vanilla checksum is correct, unsubscribe, wait a minute or two, and resubscribe to the mod. You should see the mod redownload in the steam downloads tab. If this doesn't work do a full uninstall.

This does not catch all issues but this may be faster if your download speed is slow.

It will verify all mods as well so you may want to unsubscribe from other mods to speed this up.

1) Steam -> Library -> Hearts of Iron 4 (Right Click) -> Properties -> Local Files -> Verify Game Files

Completely delete both the documents and game folder.

1) Steam -> Library -> Hearts of Iron 4 (Right Click) -> Uninstall
2) Delete `Documents/Paradox Interactive/Hearts of Iron 4`
- Copy any saves you want to keep before deleting
3) Delete `.../steam/steamapps/common/hearts of iron 4`
4) Reinstall the game via steam