Whenever when you attempt delete or edit any user or resource on the GroupShare 2017 website, you receive following error:
An unknown error occurred!

e.g. for a TM



Or, when you are trying to edit/add a new TU to any server TM you receive the following error message:

- in the Editor view when confirming segments:
An error occurred while using the translation provider [TMname]: One or more errors occurred.

- in the Translation Memory view when Committing Changes on server TMs:
One or more errors occurred.
Response status code does not indicate success: 404 (Not Found).

Note: In the IIS logs, the corresponding requests are logged with status code 404 - substatus 6.

Unblock HTTP verbs

1. Open Internet Information Services (IIS) Manager
2. Select instance node
3. Double click Request filtering
4. Go to HTTP Verbs
5. If any standard HTTP verb is listed as Allowed False (specifically DELETE or PUT), Remove that entry

Further, you may want to ensure that under Edit Feature Settings, Allow unlisted verbs is enabled - or that all standard HTTP verbs are explicitly allowed.
 

Unblock HTTP DELETE method in Firewall

HTTP verbs PUT and/or DELETE blocked on IIS instance