not receiving notifications for new responses on group forms
I am not receiving notification of new responses on group forms. "Email notifications on new responses" is checked.
This is (probably) because your Office 365 Group mailbox has the (default) setting of "Allow external senders to email this group" disabled.
When a Form is submitted, an email is sent from the address email@example.com to the Office 365 Group mailbox, if you check your message trace you might find errors such as:
Error: 550 5.7.193 UnifiedGroupAgent; Delivery failed because the sender isn't a group member or external senders aren't permitted to send to this group.
I've added a comment to the following suggestion: