We are tearing our hair out with this problem.
Some of our Macs (random, not always the same) are not checking in with the JSS on the 15 minute Check-in Frequency set under Computer Management. This means that when a policy is available it takes sometimes hours and even days for the policy to apply to all the Macs (currently around 40 as we're still in early stages of rollout).
Our network admins say that all the ports are open to APNS. What are some of the reasons why some Macs might not be checking in? We have verified that they are turned on, plugged in (wired not wireless) and not sleeping.