How to set up call forwarding (Bitrix24 -> VoIP gateway GrandStream GXW 4224 -> Analog phone)?

Question

Telephony

Good time of the day.
When introducing Bitrix24 into corporate logic, a problem arose. The problem is that it is not possible to transfer the call using the FLASH button , we thought that the problem was in the phone, but soon found out that all analog phones do not transfer the call. Translation using SIP phones is great, translation using the Bitrix24 web interface also works. The problem arose when telephony was connected to Bitrix24 , before that there was a transfer using FLASH Worked on Samsung OfficeServ 7200 PBX (which was thrown out), SIP phones are attached to Bitrix24 detailsdirectly, and analog ones through the FXS ports of the GrandStream GXW 4224 gateway , where each port, in turn, is directly connected to the Bitrix24 details .
The actual implementation of connecting analog phones:
MCN (provider) -> Asterisk -> Bitrix24 -> GrandStream GXW 4224 -> Analog phones
Analog phones -> GrandStream GXW 4224 -> Bitrix24 -> MCN (provider)
Maybe someone faced a similar problem?