Thank you for reaching out. I can certainly understand your frustration with your steps not syncing between your Gear S2 and your Galaxy S21 FE and would be happy to look into this further for you. If your Samsung Health data isn't syncing automatically between your watch and phone, you should check your network connection and make sure the app is updated. If your watch was set up without a phone, then your most recent activity is stored only on the watch and you will not be able to view it on your phone. Give this link a try for troubleshooting steps for Samsung Health data not syncing: https://www.samsung.com/us/support/troubleshooting/TSG01003270/
If you have tried the troubleshooting steps and are still experiencing these symptoms, I would recommend reaching out to our Samsung Health team directly at (855) 795-0509 as your watch is out of warranty for further troubleshooting options.
If I remember correctly, Gear 2 is Bluetooth only, no LTE connectivity.
So long as your watch and phone are connected via Bluetooth during the activity, the phone should be comparing the data from both devices and arrive at a consensus for both to display.
If this is not happening, please check the permissions for both the watch and the phone.
