Ok i might have a (rather really odd) solution for this.
The setup: 2.1p21 CEE, regularly updated over several years (i.e. coming from at least 1.6, that is important later), distrtributed over 7 sites. Every SNMP host on all sites shows this behaviour: [snmp] success , got no information from host - CRIT but on the command line its working fine. All SNMP tuning settings fail.
I picked a random host and did a Service Configuration → Remove all and find new → Save.
Now in Monitoring view every PASSIVE check was missing, only Check_MK, Discovery and Inventory were shown. When doing a service discovery, (i.e. clicking Host → Service configuration) everything showed up, but after it was saved (again), all passive checks not showing. After one hour or so (had no SSH login for the system at the time), i did the same again, and, voila, all services showed up again normally. After saving and activating the changes, all of the “[snmp] success , got no information from host - CRIT” behaviour on ALL hosts had been gone.
Here is the Check_MK graph of the mentioned host.
Note the zigzag, then first red line is first “Remove all and new”, then nothing until second red line where i did the second “Remove all and new”. After this, the looks of the graph changes.
And here are two “Check_MK” service graphs of two of the other affected hosts. Note how the graph changes after the first “Remove all and new” on the beforementioned host:
This was all the pure “guts” feeling because at that time i was waiting for the SSH session but was too impatient, so i have no logs to prove. What i can say is that a fresh 2.1p21 installation did not have this behaviour at all, only updated from 1.6.
HTH someone
BR Thomas