I'm guessing that second Steam account messed up where things in the game point to. Just a guess. If a reinstall of OOTP doesn't work try deleting the configuration file so the game doesn't reinstall in the usual places but might instead go to wherever than thing you did moved stuff within steam. There are probably multiple threads where deleting the config file is discussed. Here's the first one that came up. Use the Search for posts and keywords to find others and see if it sounds like what is happening.
https://forums.ootpdevelopments.com/...e+delete+steam
Again, just a guess but when people try to move where the game lives on their computer, the config file is usually just needs to be regenerated. This sounds akin to that.