Scenario
A user is attempting to use the Signature 365 add-in, but a signature is not inserted into the email. On opening the add-in this is initially blank, but following a timeout period the following errors may be displayed:
Solution
This issue has been seen to be caused by a specific user setting being disabled within Exchange Online.
Navigate to your Exchange admin center, and select Mailboxes from the menu.
Select the user affected and from the flyout click the Manage email apps settings link.
Ensure that the Exchange web services option is selected - this is required for the add-in to function.
