I adopted it in iRedmail, but I cannot add a security key.

[PYU224]

I use it from iRedmail's rouncube.
When I try to add a security key, I get "Action failed: configuration is locked." and I can't add the key.

[bartnv]

I expect you are confused by the, admittedly illogical, flow of the settings page. If you have the configuration lock enabled, you need to click the slider to disable it and then click Save. Only then can you add a new security key.

I'll see if I can improve this flow a bit or at least make it clear what's happening.