We do have SharePoint list and customized using info path. Users have contribute permission and they are trying to open the form, it through error the following screen shot.
Are you using the GetUserProfileByName web service on the InfoPath form?
This issue occurs because loopback protection is enabled in the SharePoint Online environment. Loopback protection must be disabled for InfoPath forms to be able to connect to some SharePoint Online web services.
For security reasons, loopback protection is always enabled in SharePoint Online. This is a known limitation of InfoPath forms in the Office 365 SharePoint Online environment.
Method 1: You need to convert the GetUserProfileByName to .udcx file, edit it according to the Central Admin changes, upload it in Data connection library(not sure if this will work in SPO, but you can have a try).
You can refer to below article for more information:
Method 2: You can convert the request(GetUserProfileByName web service) to object model calls which does not cause a loopback.