Jamooche is entirely correct.. You need to set up as New Phone rather than using back up from an earlier Ipone. Unfortunately, it took me a lot of trouble to get to this answer.
The Apple online help and phone support was useless.. I spent much time with them, but they had no solutions, and even suggested that my Apple watch's activity application/calorie counter might be interfering.. First they checked my settings, apps, motion detector etc. Then hey told me to restart the phone. They told me to to try a restore from my backup, but they never told me to set up as new phone..
Frustrated, I then went to the Genius Bar at an Apple store for help. The first Iphone support rep did not have answers, but he brought in the Mac senior rep at the store, who suggested we try a fresh restore as a New Phone. He was just relying on a guess this might work, rather than any knowledge base, but worked. It was somewhat of a pain for me because I lost some important text conversations and all of the set-up for several business and personal email accounts. It takes some time to set up as new phone. Nonetheless it worked, and my Health monitor and application is working fine now.
I would venture to say that this information will now percolate through Apple and the answer will be more readily available when others face this issue with the health application