Pressing "#9" does not invoke the Calll Hold state
Make sure the session with the phone is considered as a PBX user.
Also check that the “Keypad Commands” option is set to “on” at the [Phone Type] page.
If your phone is using in-band for DTMF and if RTP is not relayed through PBX, PBX can not receive “#9“.
Please use SIP-INFO on your phone or set [RTP relay] = on at Brekeke PBX admintool>[Options].