You have deployed a reverse-proxy with a 'default sequence' in your forwarding hosts configuration. Your Web servers are up and running and the TCP health-checks are working, but HTTP health checks are failing.
HTTP health-checks are subject to policy evaluation. Any request that does not have a specific policy instruction or a matching forwarding rule in policy, will use the default sequence defined in Configuration > Forwarding > Forwarding Hosts > Default Sequence.
Therefore, when you have a default-sequence enabled, you could see the following issues with HTTP health-checks:
To resolve the HTTP health check failures, you must do one of the following:
Option 1) Create a VPM rule in the Forwarding Layer that instructs the health check to to go direct instead of using the default sequence that you have defined in configuration.
The rule should look as follows:
Option 2) Delete the default sequence as follows: