This problem looks like “only” a Nagios core problem.
First step i would do for troubleshooting is a look inside the nagios.log file.
If there is nothing inside then the next step is to check with an “cmk -vv hostname” if a check triggered on the command line leads to valid check results.
If the manual made check results are transferred to the core then only the “Check_MK” service stays in stale all the other services (non active ones) should have an actual check result.
From the screenshot - is there only the “Check_MK” service stale on this hosts?
What says a “cmk --debug -vvR” on the command line? No errors or warnings?
I would do these tests with an actual p15 version of 2.0.