Calls are always going to voicemail

My system is now sending all calls to voicemail saying that the extension is busy (or playing the busy greeting).

In the log, I see the problem, but don’t know where to fix it.

The log shows:

-- Saved useragent "IP PHONE 2" for peer 101

== Parsing ‘/etc/asterisk/manager.conf’: Found
== Parsing ‘/etc/asterisk/manager_custom.conf’: Found
== Connect attempt from ‘’ unable to authenticate

I see the secret value for admin in the manager.conf file - where is the other end? i.e. where is it stored and presented? When I change this back to the original value things work - how do I change it?

Passwords for phones are usually stored in sip.conf or iax.conf

This doesnt seem to be a phone password - it’s the admin/amp111 password. The only references I have is that it is set at install - is there any way to change that password later? I’ve fixed it by putting it back to amp111 but would like to change it