I have 2 IAP 305s and 2 IAP 303Hs in an IAP cluster. One of the 303H's has always been used as a mesh point. No special config, just default (short of the minimum required config). Recently I upgraded firmware from 8.8.0.2 to 8.9.0.2, and now the 303H no longer connects to the cluster.
First, I verified it still worked when wired. I reboot plugged in and it comes right up in the VC and even shows up as a mesh portal (along with the other 3). Verified firmware had installed correctly. Unplugged ethernet and powered up with the power supply and it still did not come up as a mesh point.
Did a full factory reset of the 303H, and that did not resolve the issue either.
Then I found the following mesh guide and configured a named mesh cluster individually on each AP (following the guide instructions). Rebooted all the IAPs and they all came back up, and show up as mesh portals. All show commands from the guide look correct as well.
https://community.arubanetworks.com/HigherLogic/System/DownloadDocumentFile.ashx?DocumentFileKey=248ebde3-39d4-4168-822e-512d00ce0f35
Logged into the VC when I click on Dashboard->Mesh Devices all 4 Aps show up as a portal and have the same mesh cluster name.
Thinking about reverting to 8.8.0.2. Unfortunately, I do not have a 303H console cable. Will order one if I have to.