When logging in to the GroupShare Web UI, the following error message is displayed:
An internal server error occurred. Encoding 'br' is not supported. Only gzip or deflate is supported.
The complete error message is:
This issue occurs only when connecting to the GroupShare Web UI via SSL/HTTPS.
The Internet Browser used sends requests for Brotli ('br') Encoding and this is not currently supported by GroupShare, Rest API. An Antivirus Software was enabled on the Client Machines with SSL/TLS Filtering enabled. The Request Header Accept Encoding did not specify gzip, deflate
Disabling the Antivirus or whitelisting the GroupShare URL resolves the issue.
Alternatively, the Chrome or Firefox Browser can be configured to have the Brotli Encoding disabled, or set to use only gzip, deflate Encoding.