Are they behind nat? Sounds like it might be a reinvite issue, asterisk will try to get out of the audio path by telling the endpoints to talk directly to each other. If nat is involved asterisk will often tell the endpoints to talk directly even if they have no direct connection between them.
Disabling reinvite may help if this is the case. On Sun, Apr 8, 2018, 11:27 AM Chuck McCown <ch...@wbmfg.com> wrote: > Pulling our hair out. The Aastra phones will call each other, we can send > dtmf but no audio. Linksys sip ata does the same thing. These were > working, very frustrating. >