Why does the launch screen say buy when I already have the game?

Hi, I have played this game in the past and didn’t do much because I had no clue what was going on. I decided to go back to the game yesterday ( when it was under maintenance, and at the time you did not put up the under maintenance up) and I was not able to play (because of this maintenance). I fiddled around because I didn’t know what was going on verifying and I even tried uninstalling which might have caused this. Today it says I need to buy the game which I owned previously. Please help. Thanks for your time.