After updating to Calibre 7.12.0

Hi

Ive been using Calibre for almost a year and i havent had that much problems with it until yesterday when I downloaded and updatet to 7.12.0. After installing my calibre app wont open at all regardless from where i try and open it. I couldnt go back and install a earlier version because i then get a message saying that i already have a newer version installed and to intall the previous version I have to delete and reinstall and i dont want to lose all the books i currently have in calibre.

Anyone have any help to offer?
I dont know what it is thats wrong.

TIA