Same here but I'm a stubborn mf and after a week of not giving up I've found a solution.
1,Stop all sync's with all other apps.(delete all sync Auth)
2, download Google Fit.
3, give Auth to access everything ( you know the score here.
4, turn off track activity in settings.
5, download Health Sync and authorise all the bits here.
6, open , Fitness Pal & Samsung health in background then open Health Sync.
7, go to fitness Pal and sync with FIT.
Boom jobs a good one.
After a bit Health Sync holds you to ransom but it works take my money for a good job! (Didn't cost me anything really cause I use Google opinions app and get paid for giving my thoughts). £2 odd.
Let me know if it works for you but worked a treat for me after days and days trying to find a solution (wife's not to pleased as I put lots of thought and didn't speak for days but good for you guys.
Any issues ask away and I'll retrace my foot steps.
Just and update for all of you that have not been able to get the MFP food database to sync with Samsung Health. I actually got it to work by going into Data Permissions and enabling food information and in the "Allow to Read" and "Allow to Write" areas. Before I just had it enabled for "Allowed to Read". You would think it doesn't make sense to have it enabled in the "Allowed to Write" area but it works and I'm leaving it that way. Hope this helps others.
I logged out of MFP and then went into the MFP app settings under andriod and deleted data and cleared the cahche. Then logged back into MFP and reconnected to Samsung Health. Data now flows both ways.
I have a similar problem with different circumstances.
I recently changed phones from a Samsung Galaxy S7 to an iPhone XR. I have always loved the Samsung Health app and have loaded the iOS version on to my iPhone.
I still use a Samsung Gear S3 watch, which works surprisingly well with my new iPhone. All of my workout and exercise data loads just fine from my Gear watch to my iOS Samsung Health app.
I have not been able to figure out how to sync my meal data from MyFitnessPal to my iOS Samsung Health app. The data permission and "Allow to Read"/"Allow to Write" options that were there on the Android versions of the apps don't seem to exist on the iOS versions. I know it's kind of a unique problem. Can you help with this?