SIP extensions getting "not acceptable here" when attempting to dial

[rwf]

I have totally reinstalled:
Incredible PBX 2027-U
Incredible PBX 2027-U 16.0.40 running on CrownCloud

Almost everything is working fine. My IAX2 extensions work great. My SIP phones receive calls just fine.
I just can't dial calls from them, internal or external. All I get is "Not Acceptable Here" on the display.
Using Legacy SIP right now.

The logs show the following:
[2025-06-13 01:04:29] VERBOSE[3307][C-0000012f] netsock2.c: Using SIP RTP TOS bits 184
245 [2025-06-13 01:04:29] VERBOSE[3307][C-0000012f] netsock2.c: Using SIP RTP CoS mark 5
246 [2025-06-13 01:04:29] ERROR[3307][C-0000012f] res_srtp.c: Failed to create srtp session on rtp instance (0x7f59a81efbc0) - cipher failure
247 [2025-06-13 01:04:29] WARNING[3307][C-0000012f] res_srtp.c: Could not set SRTP policies
248 [2025-06-13 01:04:29] WARNING[3307][C-0000012f] chan_sip.c: Failed to receive SDP offer/answer with required SRTP crypto attributes for audio

I have looked at the RTP settings under SIP settings and can't see anything obviously wrong but have been beating mh head against the wall.
Thank goodness I have an IAX2 soft phone for outbound and my calls come in to the SIP phone OK.

Any pointers on what might be wrong? I have Googled the message and most of the responses seem to center around trunks and not SIP phones.


Thanks

 

[dallas]

246 [2025-06-13 01:04:29] ERROR[3307][C-0000012f] res_srtp.c: Failed to create srtp session on rtp instance (0x7f59a81efbc0) - cipher failure

Are you trying to use SRTP?

 

[rwf]

Are you trying to use SRTP?

I don't think so. Or at least not that I know of. Where/how could I check?
I am seeing this on a hard phone as well as on Zoiper when trying to use SIP.

 

[rwf]

Are you trying to use SRTP?

Dallas: Here's something. I just dug into the hard phone and in the RTP settings, although SRTP was off, RTP encryption was on. I have never changed this. When I turned it off, I could call out. But since the Zoiper softphone is also doing it, wouldn't it be something they had in common (the PBX)? Is there a place in the PBX where I might have changed something unknowingly to cause this?

This is the parameter in the hard phone.

 

[dallas]

wouldn't it be something they had in common

I would have thought so. Unfortunately I'm using an old version of Zoiper Biz (2.37 with g729) - It's about 15 years old and doesn't have any srtp settings so I can't help with that.

 

[ostridge]

I don't use SRTP so not expert
For SRTP there needs to be a cetificat in the phones at both ends of the call as I understood it?