Hi Sylvie,
If you use on-premises SharePoint server, based on my search, you may firstly check the SQL server (is it stuck or out of space) and the permissions of the group which can submit forms. Moreover, we suggest you post a new thread in our
SharePoint TechNet forum for professional support. This is the specific channel that handles SharePoint server related issues and questions. Thanks for your understanding.
If the issue is related to SharePoint Online, I’d like to confirm the following things:
1.Did this form work well before? Check users' permissions in the form library. Meanwhile, as you mentioned it won’t work for all users except you (site collection administrator), please temporarily add one user as site collection administrator to check the
outcome (go to site settings -> site collection administrators -> add one user)
2.Is the Department section connected to some data sources? If you delete this section, can this form work well?
3.Do other forms have this issue?
Best regards,
Tim