Couple things you can try that come to mind:
Easiest is to flush config Steam by doing this: Exit Steam client, then Win+R (opens Run dialog); type: steam://flushconfig
This will ask you to confirm that you want to reset Steam's data, say yes (you will need to re-login to Steam and redo any Steam client settings, special beta branches, etc.). See if that does the trick.
If not, you can try a more radical option (use at your own risk!)...
Open File Explorer to where you have Steam installed; select everything except the steamapps folder and steam.exe. Then delete it all. Next go into the steamapps directory and select everything except the common folder - delete all the rest.
Go back up to where steam.exe is and run it. This will reinstall Steam fresh. If it thinks your games are gone, don't worry, they're still in the steamapps\common directory - just install them from Steam again and it'll find them during that process so you don't have to re-download everything.
