Unsent messages error on apple watch

Hi Big Sam

Try this:

• Turn off iMessage on your iPhone (Settings > Messages > toggle off).
• Restart both your iPhone and Apple Watch (turn them both off before restarting either of them):

  To turn off Apple Watch: Press and hold the side button until you see the Power Off slider; Drag the slider to turn off. To restart: Press and hold the side button briefly (until you see the Apple logo).

• If you don't already have one, create an app-specific password for Messages:
  • Go to: My Apple ID
  • Select Manage your Apple ID and sign in.
  • Select Password and Security.
  • Click Generate an App-Specific Password and follow the steps as directed.
• On your iPhone, return to Settings > Messages and turn Messages back on.

  When prompted, enter your Apple ID email address and then your app-specific password for Messages (not your Apple ID password).

• Also in Settings > Messages > Send & Receive:
  • Under You Can Be Reached By iMessage at: select both your phone number and your Apple ID email address.
  • Under Start New Conversations From: select your phone number.
• It may help to restart both devices again.

Please let me know how you get on - there are other things that we can try if necessary.

The app specific password only works with two-step verification or two-factor authentication.