The error message which says that your Doccle-account is connected to another itsme, can occur when your itsme has been renewed of if another person's itsme is connected to your account.
To replace the itsme that is connected to your Doccle account, you can log in with your username and password.
In your account, access the Settings and go to the menu Security.
In this menu, you can disconnect and reconnect itsme.