Hello @tob789. I'm sorry to hear that you're having trouble unlocking the 1Password app on your Mac and I'm happy to help.
Your 1Password account password might not unlock the 1Password for Mac app if you have migrated from using a Primary standalone vault and you're now using a 1Password account. The app will always unlock using the password of the first vault added to the app and if the first vault added was a Primary vault or part of an older 1Password account then you'll need to enter that password to unlock the app.
Can you remember if you had a Primary vault and can you try using older passwords to see if they'll unlock the 1Password for Mac app?