I have the same problem:
1. The Intelligent Hub (IH) will only talk to the server if a manual sync is done on the device.
2. Running v2001 On Prem with Sep 2020 .25 patch
3. I cannot send PIN resets, push messages, Queries, wipes, etc to the devices
4. Plenty of space on server.
5. This happens on all Android devices (Ver 7, 8, 9, 10, etc - all Samsung), HUB version: 20.08.0.23
6. Once the device is config'd it will never sync unless a manual sync is done with the IH on the device.
7. Work Managed Samsung S20 Device
8. Using Google EMM - Firebase Cloud Messaging
NOW - if I send a PIN reset/wipe, etc, and then quickly manual sync on HUB, then the reset/wipe comes through.
Also note the device shows green (last seen/enrolled, etc) when powered on.