Ok, so the above does work.... However, when you connect S Health to MyFitnessPal a progress ring will be spinning in the top right corner. When I noticed this spinning (after reinstalling multiple times) I decided to wait until the progress ring stopped. Once the progress ring stopped I exited the apps and devices screen and everything synced immediately!!!! Was getting so frustrated with this, hopefully this will resolve everyone else's syncing issues.
I'd been having the same problem with Samsung health not always syncing my step count to My Fitness Pal and after reading all the comments and trying a few people's suggestions it was still not working. I then started having a play around in the S Health app and done the follow which worked!... Not sure if it was a coincidence or actually worked!? Will see again tomorrow.
Scroll to bottom of S health home screen > click 'Manage items' > scroll down to 'feature apps' at bottom of page > click find more apps > it should then show My Fitness Pal (mine says 'open ' in green) > I clicked on it and it opened up MFP and updated the steps!...
Goodluck fingers crossed it might help some of you! 🤞☺️