When deleting an expired EdgeSyncSubscription certificate from your edge server, the following error is written in the eventlog:
The next error in the eventlog:
When the issuing certificate for your internal PKI CA has to be renewed, don't forget to renew it on the Edge servers as well.
When the Edge servers certificates for the EdgeSyncSubscription are expired, then renew the entire EdgeSyncSubscription.
A complete how to can be found here.