Hi, everything seems fine, just be sure your call to TMARSResourceRegistry.Instantce.RegisterResource<THealthCheck> takes place *before* the second call to AddApplication (in TServerEngine.CreateEngine method).
I usually make this happen adding the name of the unit where THealthCheck to the uses clause list of the Server.Ignition.pas file (in the MARSTemplate demo, you can spot the Server.Resources unit listed there for the same reason).
I am considering, in a future version of MARS, to switch from this 'initialization based' way of registering resources to a more 'configuration based' one. Still have to think about it and choose a simple approach to this problem.
Sincerely,
Andrea