To use the magnetometer with 4.4.X firmware, you must select the magnetometer option during firmware flashing.

Steps:

Re-flash the firmware, and during the flashing process, enable “Magnetometers” under Other Options.

Once flashing is complete, the magnetometer will work.

Refer： https://docs.speedybee.cn/fpv/fc-flight-controller/flight-controller-faq/how-to-properly-flash-betaflight-firmware-version-4.4-and-above.html