In your config , under voice register pool 1 , TYPE and DESCRIPTION are missing.For example : voice register pool 1 id mac C414.3C96.A277 type 9971 ----------------------------> missing number 1 dn 1 dtmf-relay rtp-nte username sctwo password ci...
You can use device pack to add the phone button template for phone 7821. Also, you can install the first device pack for 7821 or can use the latest device pack. Both should work.Installing the latest device pack is recommended though.
I believe those 80 users are already registered with anther node of the same cluster , may be with PUBLISHER. If that's the case, then you can go ahead and safely install a new SUBSCRIBER to this Cluster.There wouldn't be any impact on those register...