Hi SikrestIQ,
In the active/standby AC scenario, the standby AC should be upgraded first, and then the main AC should be upgraded to protect services from being affected.
If the AP is not online, it is recommended to use the automatic upgrade method to upgrade. If the AP is already working online, it is recommended to use the online upgrade method to upgrade.
Before upgrading APs, ensure that all APs to be upgraded are in the ver-mismatch, normal, or config-failed state. In addition, when the AP is in the config-failed state, the AP can only be upgraded automatically, but cannot be upgraded online or scheduled. You can run the display ap all command on the AC to check the AP status.