Can't launch Fallen Order on Steam; "The game does not appear to be installed."

I've played through the entirety of Fallen Order previously without issue and recently wanted to replay the game, but it's acting up for some reason now...

I first launched it late at night to test and make sure it was working in which I was able to get to the title screen without issue. I then proceeded to play some of the tutorial level the following morning before work in which it also worked just fine. Then I got back home from work and the game suddenly was telling me it wasn't installed?? It ran twice without issue and just stopped working?

I don't particularly remember how, probably a weird combination of uninstalls and reinstalls, but I managed to get it working after a couple of hours of throwing sh** at the wall trying to get it to work and proceeded to play the rest of the tutorial level, completing most of Bogano and some of Dathomir. Fast-forward to today and now it's doing it again and I refuse to sit here for another three hours bashing my head against the keyboard until it decides to work again.

Anyone know of a reliable, permanent/semi-permanent solution or will I have to put this up with the Origin support team?