My Forerunner 35 connects OK with my iPhone 12 , Garmin Connect.
But it used to sync with Life Cycle App showning running times (I don't carry my phone on runs).
Then it stopped and I have to enter the times into Life Cycle manually.
I tried to reboot (Singificant location) on the iPhone and I reinstalled Connect, but no joy.
Does Garmin interface through Apple Health?