After upgrading to 11 MP1, 11.1 MP1, and 11.5.1 red exclamation marks ("!") on protocols in Traffic report saying the servers needs to be upgraded.
However, the Enforce and Detection Servers are on the same V11 version and properly upgraded.
"! Servers marked with this icon require upgrading. Until upgraded, only minimal functionality will be available and a server restart will disable all functionality."
This error is just a cosmetic problem that does not have any effect on the actual working of the product.
As reference we have filed Etrack 2407307 ( V 11.0 MP1 ) & 2407309 ( V 11.1 MP1 ).
Further verification could be to make a policy change for one of these two monitors and then generate incidents that would only happen given that policy. If the incidents appear in Enforce, then the monitor is not down-level from the Enforce Server’s perspective and properly operating at the same version level.