I am sorry to hear you are having this issue. For this, I would recommend trying these additional steps:
Is the HR on the back of the watch lighting up? If not, do you have this enabled in the watch menu? Try toggling this off, then on again.
Do you have the watch in battery saver mode? This can also disable the HR sensor. Try disabling this.
You mentioned restarting the watch. I would also recommend a hard reset specifically. For this, hold the Light button until the watch shuts off, as opposed to selecting power off. Then power this on again.
If this is still not displaying the HR, ensure the sensor software is listed in the watch. Menu, System, About, Scroll down. Ensure the versions are listed for Sensor Hub, WHR, and BMX. If any of these are showing as 0.00, this is missing. For this, I would recommend syncing with Garmin Express.
I would also recommend trying a factory reset with these steps:
Ensure the watch is powered off.
You may need to hold LIGHTfor up to 30 seconds to turn the watch off.
Press and hold BACK and START/STOP.
Press LIGHT to power the watch on while holding these two buttons.
After the first beep release START/STOP.
After the second beep release the remaining button.
If the issue continues, I would recommend contacting Garmin Product Support, as the watch may need to be replaced.
