The Symantec Endpoint Detection and Response (SEDR) appliance reports that "the Symantec EDR is Critical" that the SEPM is unavailable.
When reviewing the "Endpoint Communication Channel, SEP Policies, and Endpoint Activity Recorder" EDR reports an "Authentication Error" similar to the following.
Attempting to refresh the SEPM controller connection results in a "Error: SEPM returned 500 internal server error status code".
Attempts to navigate to https://<IP_OF_SEPM>:8446/sepm result in a 500 error as well.
When clicking on the Advanced Security tab in SEPM 14.3 RU3 an authentication error is shown.
SEPM: 14.3 RU3
This issue was resolved via LiveUpdate on 11 December 2021. If this issue re-occurs please open a case with Broadcom Technical Support.