I have not received any server side events since Wednesday 20th August 5:30pm BST and I wondered if there is an issue with the cloud or something has changed with this API?
I updated my cores deep firmware this morning just to be sure that was not the issue and it does not seem to have fixed it.
Normally this means that your access_token has expired. Try getting the events using curl and see. Or you can use the Spark CLI or API calls with curl to manage your tokens.