If you’re like me and you have the radio app not working and your Apple Watch is saying: “Sign in to your Apple ID in General in the Apple Watch app on your iPhone” (And of course you are signed in), this solved my issue.

• Go to “Settings -> iTunes & App Store”
• Tap on your logged in Apple ID.
• Tap Sign Out button.
• Reboot your phone (Just in case!)
• Go back to “Settings -> iTunes & App Store”
• Log back in with your Apple ID
• Go to you Apple Watch and most probably you’ll see Radio working! Hurray!

Apple Watch Series 4 just in case. 😉