ATCOM AT530P and UNHOLD problem

I have problem with AT530P after updating to Asterisk UNHOLD stops working. (UNHOLD worked with Asterisk

A - AT530P
B - PSTN/SIP Provider/Phone from other vendor (f.ex. X-Lite, Grandstream)

B call A.
A pick up the phone.
A press Hold and hear tone, B hear music.
A press Hold again and can talk, B hear music.

Please help me :smile:

Michal Januszewski