Once Form Publisher is set up on a Google Form, the only account that can configure the add-on is the account which set it up in the first place. Sometimes, the owner of Form Publisher on a specific Form wants to transfer the ownership to someone else. But there is no button that allows ownership transfer in the add-on. You will find below how to transfer your ownership to another account.
Go to the Form Publisher Status option in the add-on menu:
Disable the add-on in the sidebar:
This way, Form Publisher will erase the current trigger and the ownership of the add-on. Then, the person who needs the ownership must log in with their own account.
Note: This new account must have the permission to edit the Google Form in order to have access to the add-on menu.
Once the Google Form is opened, select Form Publisher Status option in the menu and re-enable Form Publisher.
And that's it! The account that has re-enabled Form Publisher has now access to the sidebar.