When we release a new version of Form Publisher, new permissions might be added. If you do not reauthorize Form Publisher, then the add-on will stop working (including files generation, sending emails etc.).
Form Publisher will send you an email to inform you about this new authorization.
What you have to do next is to open your Google Form, go to Form Publisher through the add-on menu, then click on Status & quotas.
A new window will pop up, click on Allow to accept the new permissions.