We are testing 3rd party monitoring application and seems that service is not starting if there is no internet connection on the server. If we allow internet for a minute, service starts then, even if we disable the internet afterwards service will start later.
Developers says they are not aware of this issue. There is no call home feature in software.
Service is digitally signed, so I assume it is maybe checking the certificate with certificate authority? Anything else that I need to look for, why the service needs internet connection for the first time to start?
I'd make this the developer's problem as its their application performing badly - telling you that they're unaware of the issue is pretty bad as the most likely explanation is quite well known: The system is possibly trying, and failing to check the validity of the certificate with its provider's certificate revocation list. You need to disable certificate revocation checking.
Install the application on another server and if the problem exists there as well as on the first server then I'd say that puts the problem squarely in the vendors lap.