The IP to our vcenter server changed and not I can't get appliance unregistered to then register it to new vCenter ip...
Extension management error: Cannot complete login due to an incorrect user name or password
Any help would be great!
Can you check if file /opt/vmware/etc/vami/ovfEnv.xml inside the VR appliance is present and not empty?
If it is empty - please power off the appliance and power it on through vCenter Server (power on directly through client connected to ESXi won't populate the OVF environment). Power off/on is required, restart won't help.
Without the OVF environment, VR does not have the token to register its extension into vCenter Server.
Also, changing the IP address of vCenter Server does not require unregistering VR from vCenter and registering it again (Reconnecting Sites Fails If One Of the vCenter Servers Has Changed Its IP Address). Simply a "Save and Restart" from the VAMI UI is enough (after verifying the address of vCenter Server displayed there). The default value for the vCenter Server FQDN/IP address is taken from the OVF environment (/opt/vmware/etc/vami/ovfEnv.xml populated on appliance boot from vCenter DB).