1, For prerequisite check warning, please try to remove the NNA and add a new one with only the required permissions and run prerequisite check again.
This reference link for your reference:
Note: Microsoft provides third-party contact information to help you understand the problem. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
2, However, the client device displayed as unreachable may be caused by other reasons.
(1) Please upgrade to the new version again and check if the problem also occurs.
If the problem recurs, please help check if the server version has been completely upgraded and if there are any other issues. Besides, if there are any other issues present, please help upload CMUpdate.log for our reference.
To check SCCM version we can refer to this link:
Complete SCCM 2303 Upgrade Guide | Update to ConfigMgr 2303 (prajwaldesai.com)
Note: Microsoft provides third-party contact information to help you understand the problem. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
(2) Please help check whether your "Fast Channel Push Notification" works properly? Please help check the following logs to see if there are any error. If so, please upload full log for our reference.
- Notification manager(Located in site servers): BGBmgr.log.
- Notification server(Located in MP): BGBServer.log.
- Notification Agent(Located in client): CcmNotificationAgent.log and locationservices.log.
This similar case for your reference:
SCCM Client icons showing offline - how to fix this? - Microsoft Q&A
Looking forward to your feedback.
Best regards
Cherry
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