We had to move the primary and standby servers to another network.
I found an old thread about dong an update of repl_nodes but I wasn't sure if applicable for my version.
repmgr primary register -f /path/to/repmgr.conf - which has the correct conninfo details.
and all looks good under "cluster show".
No luck on the standby doing the equivalent and it shows the wrong fqdn for the primary under "cluster show".
Standby did not like an "unregister" attempt.
pg_hba.conf looks good on both ends.
Not sure what needs to be done/how this should be approached. Would appreciate some magic commands please.