The solution for this is as follows:
1. Go to Management Console > Settings > Parameters and search for CSTA_USER_AGENTS Parameter .
2. Replace the value of this parameter with the value below:
Fanvil X,Fanvil C400,Fanvil C600,Fanvil H,Htek UC8,Htek UC9,snom3,snomD,snom7,snom8,Yealink SIP-T19P_E2,Yealink SIP-T19_E2,Yealink SIP-T23,Yealink SIP-T27,Yealink SIP-T29,Yealink SIP-T4,Yealink SIP-T5,Yealink SIP-CP920,Yealink SIP-CP960,GrandStream GXP2170,GrandStream GXP2160,GrandStream GXP2140,GrandStream GXP2135,GrandStream GXP2130,GrandStream GXP17,GrandStream GXP16
3. Restart all PBX services