Hi! Indeed, at least the error message is not correct. I remember this thread Enable HA does not work when juju controller machine has multiple subnet ips/nics - #9 by mastier1. The error is not exactly the same, but it might give us some hints regarding what’s going on.
What juju version are you on? Also, could we get the outputs of juju spaces, juju subnets? I see that the nic in the machine indicates the correct space, but there might be some inconsistency maybe.