In order to have the Policy Server failing over to the next Policy
Store, the first Policy Store should not be reachable. As good practice,
when you detect a problem on a Policy Store service, shut this service
down. The port won't be reachable and as such the Policy Server will
failover to the next Policy Store available.
If the Policy Store still has its port open, but has problem to
give answer, the Policy Server will keep trying to contact it.