Theres a known bug that you cant configure from the UI. From the CLI it should work.
I am running 8.12.0.5
(MC1) [mynode] #configure t
Enter Configuration commands, one per line. End with CNTL/Z
(MC1) [mynode] (config) #read-bootinfo ap-name ap6341
(MC1) [mynode] (config) #pro
process Process level operations
prompt Change the system prompt
provision-ap AP provisioning
(MC1) [mynode] (config) #provision-ap
(MC1) [mynode] (config-submode)#a-ant-gain
<a-ant-gain> Gain for 5.2GHz (802.11a) antenna
(MC1) [mynode] (config-submode)#a-ant-gain 6
(MC1) [mynode] (config-submode)#g-ant-gain
<g-ant-gain> Gain for 2.4GHz (802.11g) antenna
(MC1) [mynode] (config-submode)#g-ant-gain 6
(MC1) [mynode] (config-submode)#x-ant-gain
<x-ant-gain> Gain for 6GHz (802.11e) antenna
(MC1) [mynode] (config-submode)#x-ant-gain 5
(MC1) [mynode] (config-submode)#reprovision ap-name ap6341
(MC1) [mynode] (config-submode)#write mem
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Original Message:
Sent: Dec 18, 2025 06:09 AM
From: sboutreau
Subject: AP-634 External Antennas will NOT work
This config doesn't work for me : I've got the same message than above