Are all the APs in swarm mode (not standalone or single)?
Could it be that you have an IP conflict for the VC Cluster IP address?
If you can login to one of the APs, a 'show log system' from CLI or WebUI may give an indication of what is wrong. From the information provided, I think it is impossible to find the reason.
What is the AP type?
Firmware version?
Do all APs have the management VLAN untagged on the switch (recommended)?
Are all APs configured to get their IP through DHCP (recommended)?
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Herman Robers
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If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check
https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
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