New MSP, can't hear client when we call

[Generic Network Systems]

Hello All,

We (the new MSP) just took over a new client's 3cx system. We've never worked with 3cx before so this is all new to us. When we (MSP, on Asterisk) call our client (the 3cx system), they can hear us, but we can't hear them. When the opposite occurs, the call is fine and everyone can hear each other. They have no other reports of this happening with their calls. Any ideas on why this is the case?

Not sure how much / what info is needed here, but I'll start with the below. If any other info is needed, let me know.

• 3cx portal says the system is Self-managed
• Local telecom provider is listed as a SIP trunk in admin console
• There's a local desktop in their office that's apparently running a "Session Border Controller". Not sure what this does, and wasn't able to find any launchable 3cx programs on it.

 

[Noel Evolution]

You might have to tick the "PBX delivers audio" on the extension options.

 

[Generic Network Systems]

You might have to tick the "PBX delivers audio" on the extension options.

Hmm, that doesn't appear to have fixed it, although I'm not sure if this change is immediate or takes some time to propagate.

some additional info... they only have their main line as a call-in number. no call tree or options to dial an extension. No direct dial numbers either.

 

[Evolute IT]

Could be a provider issue if they're using a local one that's not supported/validated on 3CX.

I suggest you subcontract a 3CX Partner to diagnose and help you figure this one out. Perhaps learn of 3CX in the process.

By the way, the SBC is for deskphones, it's like a VPN proxy that takes all phones traffic and sends it as one feed to the PBX via an encrypted tunnel.

 

[SteveITS]

When nobody’s on a call run the firewall checker in 3CX. It restarts services.

I was also going to post it could be a SIP provider issue, probably more so if limited to specific numbers or certain other providers. A packet capture should help find whether the audio is leaving 3CX.