MiCollab: One-way audio for internal calls only

[synthesis]

I am experiencing a strange issue with an end user using MiCollab client 7.3. When calling an internal extension, they can hear the other side but the other side cannot hear them. However, when calling an external number, e.g. mobile number, both sides can hear each other. I tested this by calling the internal number of reception where there is one-way audio, but when dialing the external number of reception both sides can hear each other. What could be the cause of this issue?

[sunspark]

Internal call ok, but the phone are in the same place or on two different sites?  99% of one way audio problems are related to the firewall.

[synthesis]

Internal call ok, but the phone are in the same place or on two different sites?  99% of one way audio problems are related to the firewall.

The phones are in the same site. The only firewall being used between the communication is Windows firewall. I think it wouldn't be a firewall issue as there is no one-way audio when the MiCollab client (with the issue) communicates with an external number.

[sarond]

Are phones and PC's on same subnet?

Could be a routing issue as the 2 endpoints need to be able to communicate directly.

[synthesis]

Are phones and PC's on same subnet?

Could be a routing issue as the 2 endpoints need to be able to communicate directly.

Yes, it was a routing issue as the phones and PCs are on different subnets. Had a static route on the MiCollab PC only pointing to the IP of the PBX (which is on the same subnet as the phones). Changing the static route to point to the subnet of the phones solved the issue.