HA The backup firewall is not accessible (check user credentials)

[Igor]

Hi.
(Following this thread), to fix this here I reconfigured:

On Master:
- System > High Availability > Settings = Synchronize Config = 10.0.0.2:443  # added the :443, 10.0.0.2 = backup
- System > Settings > Administration = Listen Interfaces: All (recommended)

On Backup:
- System > Settings > Administration = Listen Interfaces: All (recommended)

[bamypamy]

I had the same problem. Here is what fixed it for me.

I did an update from 24.4.3 to 25.4.1 (VMs on proxmox).
I'm not using the default web GUI port, but I've never had to add the port to the IP settings in the HA configuration.
I have tried though, but it didn't help.

Since my firewalls don't have direct internet access, I had added the proxy environment variable as shown here so I can download updates.
https://docs.opnsense.org/development/backend/configd.html#extending-the-environment

That worked fine, but it broke the HA synchronization.
I can reproduce it. When I create the proxy.conf and restart configd, I immediately get the error message on the HA sync status page.
If I delete the proxy.conf and restart configd, I immediately see the status of the cluster again.

Maybe it will help someone else and save them from getting (even more) gray hair.

[xtom42x]

Since my firewalls don't have direct internet access, I had added the proxy environment variable as shown here so I can download updates.
https://docs.opnsense.org/development/backend/configd.html#extending-the-environment

That worked fine, but it broke the HA synchronization.

That setup is very close to mine (#14) - proxmox VMs, no internet and proxy - so the proxy settings is likely the culprit to look at