Apple Watch - Nike Running App

Hi,

I recently purchased an Apple Watch - the series 6 Nike version (GPS only) (UK) at start of Jan 2021 . I have been really happy with it. I was using the software on the apple watch that came with it, so likely to have been the software version prior to 7.3. Last week I reluctantly decided to update the software up to 7.3. I did a run - 5th Feb 21 - using the Nike Running Club app on the watch where I can see that it recorded the run in the nike running app on the watch, but did not record it in the Apple Fitness app for some reason. I've tried resetting the watch but the run does not show up in the Apple Fitness app. I'm not particularly impressed when I've spent £400 on a watch that doesn't record my data. Prior to the update to 7.3 software, I had no problems with runs being synced but as soon as I update the software this occurs. Any advice would be gratefully received.

Kind regards

Nick