I really like the Grandstream access points. However, their documentation is not very informative. I tried to upgrade my GWN7660 AP and it kept failing. If you have your Manager/Controller on a different network, it is not as easy as the vendor shows it in their demo.
I am using OPNsense as my firewall and I have the Manager on a different subnet/VLAN. The access points have their own subnet/VLAN because I like it that way. To get this working, I added the port 8443/tcp to the ruleset between the AP and the Manager.
# AP adoption 10014/tcp # AP upgrading 8443/tcp
Hope you’ll find this useful. Cheers!