I spent 1hr and 45min on the phone with Apple Support. I ended the call without a solution because they had no clue (despite their genuine efforts). So far, I've done the following to no avail:
Hard reset of the watch
Turned off watch multiple times
Unpaired watch from phone
Turned off bluetooth multiple times
Deleted fitness app from phone
Reinstalled fitness app to phone
Signed out of icloud
Disconnected bluetooth AirPods
Forgot AirPods from bluetooth settings
Turned off phone multiple times
None of these things worked for me. I have an iPhone 8+ and the second (or third?) generation of Apple Watch. Perhaps it's something to do with the software and the fact that my devices are old. I don't know, and sadly, I don't care anymore. I am so disappointed I have to walk away. 1hr and 45mins and still no one can recommend a solution... (Note: all other BT devices work just fine, Homepods, Apple TV, etc.)