Playing offline and invalid session error.

Whenever I load the Minecraft Launcher, it only says "Play Offline" no matter what I try. I load up Minecraft itself and all it says is "Invalid Session" without an error code or anything. I was hoping there was a fix.

Edit: I have tried everything from reinstalling to reconnecting to the internet and even restarting my PC. Nothing seems to work.

Second Edit: I have tried to play online in other games on my PC and it works just fine. Even using my Mojang account (Which I haven't migrated yet) works. I can go online on that account and play on servers and all that. I would use that account and just forget about this one but I have lots of stuff that I bought on my Microsoft account for Minecraft. I hope there is a quick and simple fix.