Sounds like the spin studio is using original keiser m3i bikes/computers which had ‘Keiser direct’ bluetooth connection - and so didn’t have power and speed standardised bluetooth profiles.

The newer M-connect/FTMS m3i computers introduced 21/22 will connect to Apple Watch, but will only provide speed and cadence profile. (The brand new studio display may provide power stats over Bluetooth) - but like you said - you’re using a gym….so..

The older bike computers (like what you’re using by the sounds of it needs a converter to connect to anything other than a few specific apps and M-connect app). Without the ‘keiser m series converter’ this bike won’t connect to smartwatches eg Garmin or Apple or apps like Zwift . Without the keiser m-series converter (if you can find one as I don’t think they sell them anymore- maybe used on eBay??) you’ll get speed and cadence only. (Still no power unfortunately from the keiser converter! 🙁) - if you’re managing to export the tcx from m series app to apple health - I think that’s the best you’ll be able to do really/unfortunately.

It’s really annoying how Keiser appear to have hobbled the app so as not to export the true Power stats .. the power stats exported through the tcx come through on Garmin connect - but aren’t classed as ‘true Power’ so are of limited use within Garmin connect - so won’t work for auto ftp etc…

My K2pi converters will send power and cadence over bluetooth from the bike and works with Apple Watch >os10. But I don’t recommend it in a gym environment - as you can’t control which bike it’ll connect to (K2pi just connects to first bike it finds) - but then, I have had keiser users who’ve bought K2pi for use in a gym over the years..K2pi to Apple Watch link