...
Notify the external user of the file type error and teach them on how to submit correctly.
To fix the issue internally:
Transition the activity with the incorrect file/activity type to Closed/Submitted in Error or other another end state.
If you think a transition option is missing, please submit a help desk ticket.
Wait for the external user to submit correctly or follow the remaining steps to create a new activity for the external user.
Leave all files on the original activity, but download copies, which you will put on the new, correct activity type.
Staff may use the submitted date of the original document for compliance purpose if the only thing wrong with the submittal was the activity/file type.
Create the proper activity type, upload the files to the new activity and choose the applicable file type for the document(s).
Link the original activity to the new activity. For guidance on linking, visit How do I link activities together?
Process the submittal on the new activity.
...