The Yealink WF50 is only compatible with the following phones

• Yealink SIP-T27G
• Yealink SIP-T41S
• Yealink SIP-T42S
• Yealink SIP-T46S
• Yealink SIP-T48S
• Yealink SIP-T42U
• Yealink SIP-T43U
• Yealink SIP-T46U
• Yealink SIP-T48U
• Yealink SIP-T52S
• Yealink SIP-T54S
• Yealink SIP-T53

The Yealink phone must also be running version 84 firmware otherwise the WF50 USB Dongle will not be detected by the phone.

At time of writing the following firmware should be running on the phone

• Yealink SIP-T27G requires firmware (Version 84 or later) latest Yealink Firmware is 69.86.0.15 and latest 3CX Firmware is 69.86.0.5
• Yealink SIP-T41S requires firmware (Version 84 or later) latest Yealink Firmware is 66.86.0.15 and latest 3CX Firmware is 66.86.0.5
• Yealink SIP-T42S requires firmware (Version 84 or later) latest Yealink Firmware is 66.86.0.15 and latest 3CX Firmware is 66.86.0.5
• Yealink SIP-T46S requires firmware (Version 84 or later) latest Yealink Firmware is 66.86.0.15 and latest 3CX Firmware is 66.86.0.5
• Yealink SIP-T48S requires firmware (Version 84 or later) latest Yealink Firmware is 66.86.0.15 and latest 3CX Firmware is 66.86.0.5
• Yealink SIP-T42U requires firmware (Version 84 or later) latest Yealink Firmware is 108.86.0.70 and latest 3CX Firmware is 108.86.0.72
• Yealink SIP-T43U requires firmware (Version 84 or later) latest Yealink Firmware is 108.86.0.70 and latest 3CX Firmware is 108.86.0.72
• Yealink SIP-T46U requires firmware (Version 84 or later) latest Yealink Firmware is 108.86.0.70 and latest 3CX Firmware is 108.86.0.72
• Yealink SIP-T48U requires firmware (Version 84 or later) latest Yealink Firmware is 108.86.0.70 and latest 3CX Firmware is 108.86.0.72
• Yealink SIP-T52S requires firmware (Version 84 or later) latest Yealink Firmware is 70.84.0.70 and latest 3CX Firmware is 70.84.0.80
• Yealink SIP-T53 requires firmware (Version 84 or later) latest Yealink Firmware is 96.86.0.70 and latest 3CX Firmware is 96.86.0.74
• Yealink SIP-T54S requires firmware (Version 84 or later) latest Yealink Firmware is 70.84.0.70 and latest 3CX Firmware is 108.84.0.80

Firmware can be downloaded directly from Yealink here:

Yealink Support

If you are running 3CX then you can download the latest supported firmware from here:

https://www.3cx.com/support/phone-firmwares/