lost my progress after syncing

If you've merged your accounts, you can continue playing with your previous characters and progress by choosing the sub-account that corresponds with the account you were previously playing. You can choose which sub-account you're using on the character select screen, so if you haven't made any characters yet on the currently active sub-account you may want to try making a character and returning to character select so you can switch over to your other sub-account.

You may have the old account selected when playing, so you'll want to try creating a new character so that you can swap between sub-accounts at the character select screen as mentioned. I hope this helps!