If I understand correctly, the dial-in users (PPP and/or exec) can authenticate fine when authentication is configured locally on the as5300. That means you have issue authenticating with the external AAA server.
1. What server is used? RADIUS or TACACS+?
2. Since you moved locations did the IP address of the ethernet change? Can you ping the AAA server from the as5300? If yes, on the AAA server have you changed the NAS ip address pointing to the new ip address (since location change)?
3. From the as5300 you can try the following command test aaa group legacy. Use a username/ password that is already configured on the AAA server.
4. Can you please post the sh run outputs.
Can you please run the following debugs for a call that fails:
Deb modem / deb modem csm / deb ppp nego / aaa authen / deb aaa author / deb radius or deb tacacs
Thanks, Mak