If you have steam cloud sync activated, please turn it off, then locate your save files in the 'C:\Users\<UserName>\AppData\Local\Larian Studios\Baldur's Gate 3\PlayerProfiles\Public\Savegames\Story', and save them in another folder where you can find them easily.
Proceed to launch Baldur's Gate 3, and it should act like it's your first time opening the game. Close the game, and re-enable the steam cloud and then open the game again and let the steam cloud saves load again.
Let me know if this method worked for you.