After a Prism Central upgrade, IAM authentication settings may require reconfiguration.

Option D (Log in with a local admin account) is correct:

If IAM authentication fails, thelocal admin account must be usedto check domain settings.

Option A (Ping the Domain Controller) is incorrect:

Network connectivity is important, but theissue is likely related to IAM settings, not network reachability.

Option B (Check firewall port 9441) is incorrect:

Port 9441 is used forSSO authentication, butport issues usually result in login delays, not complete failures.

Option C (Validate signing certificate) is incorrect:

While certificates can cause issues,local admin login should always work.