How to disable & enable HA
If went to change something as like network configuration, it is need pasue/disable HA model first, and following steps for your reference:
How to disable HA:
Login HA "ACTIVE" NAS -> HA page -> DISABLE -> choose DISABLE both NAS -> both NAS would auto reboot.
How to enable HA:
Login "both" HA NAS at same time as possible -> HA page -> ENABLE -> would asking "HA RECOVERY" choose "NO"! -> both NAS would auto reboot into HA mode.