Since the last firmware update, I haven’t been able to make outgoing calls on a DP752. Incoming calls are fine, and calls via a soft-phone to the VoIP provider are fine, it’s only the DP752 that can’t make a call, and it’s only happened since the last firmware update (although this may be a coincidence, I rarely make calls and it could have been a change at the VoIP provider). The provider has been trying to resolve this without much success.
What’s happening is that the soft-phone is going through the expected INVITE -> 401 -> ACK -> INVITE -> Trying sequence of placing a call, the DP752 instead has INVITE -> 401 -> ACK -> INVITE repeated three times after which the call fails. The only significant difference I can see between what the soft-phone and the DP752 are sending is an a=crypto in the SDP offer, but I can’t see that that would make any difference.
Does anyone have any ideas what the problem could be? There’s been a few other posts on the 511 problem but nothing in the replies seems to apply in this case.