Looks like the cron is not triggered then as it should. I have tested the cron event on a server, but everything seems to be okay in terms of it’s registration for execution. I suspect that either something is clearing the cron-jobs, or preventing their execution. Once the cron is registered, it is up to wordpress for execution.
May I ask what timeframe is the cron set to be executed? Can you try the lower values, like 5 minutes or so? If there is something regularly clearing the cron jobs, that might prevent that.