MacOS Server Push notification not working

[Mrpower]

I have noticed that my MacOS Server is not updating profile or push update to computers or tablets as it should be doing. In Profile Manager, under the activity tasks Menu, all of the tasks are pending and they never complete. I believe it has something to do with apple Push Notifications. It was all working earlier in the week and now it has stopped. Has anyone experienced this or do you have any advice on getting it up and running again?

[Brimstone]

Has your APNS Cert expired....?

[Mrpower]

Nope. But I have managed to resolve the problem by simply restarting Profile Manager and the web server on the server, which seems to have done the trick. However it would be nice to know why it did it in the first place.