WatchOS 3/iOS 10 - Activity/Apple ID issues

not sure if there's a connection but my Apple ID doesn't seem to be signing in on iPhone (Watch app > General > Apple ID) just getting the spinning loading circle

See if resetting your Apple ID password helps.

You can reset your password when you go to your Apple ID account page and click Forgot Apple ID or password.

Hi

The following steps have previously resolved Activity data sync issues for others.

However, note that they result in the permanent loss of all existing sensitive data on your iPhone and watch, including all historic Activity and Health data, HomeKit data and saved passwords.

• Start by making an unencrypted backup of your iPhone:
  • This must be done via iTunes on a computer (because iCloud backups are encrypted as standard);
  • Do not select the option to Encrypt iPhone backup;
  • How to back up your iPhone, iPad, and iPod touch - Apple Support
• Restore your iPhone as new (ie to factory settings) using iTunes:
  • Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings - Apple Support
  • When you see the option to Restore or Update, choose Restore;
• After the Restore completes, during setup, restore your iPhone from the unencrypted backup;

  Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

• Pair your watch, setting it up as a new watch (do not restore it from backup):

  Set up your Apple Watch - Apple Support

If you have historic data that you wish to retain, another option to consider is unpairing your watch and then setting it up as a new watch.

You are most welcome - thanks for following up! 🙂