Cannot sign into iCloud

Message activation error

Have someone else attempt to sign in using their Apple ID. If they can successfully sign in and use Messages/FaceTime, it may be your Apple ID.Someone I know had this happen and I was able to sign in usingmy Apple ID. After a call to Apple Support and then being elevated to a tier 2 support person, it turned out it was a problem with their Apple ID. It took the software engineers 3-4 days to fix the problem. When calling Apple, make sure you tell them it is an Apple ID problem so you don't get charged.

There is a contact link.

Apple ID Support

Apple ID Support (2)

Apple Support by e-mail or chat Select your device, Battery, Power and Charging, then Power adapter not working to get a chat option.

Apple Support using Twitter

Or fill out and submit this form.

You wrote

Deleting the contents of my keychain.

If the entire contents of keychain are deleted from user library , then its a mistake made you have to reinstall the Mac OS see this article https://support.apple.com/en-in/HT204904

You are welcome. If FaceTime works on your devices, it isn't an Apple ID problem.

Handoff Continuity Troubleshooting

Handoff Continuity Troubleshooting (2)

iPhone, iPad, iPod touch, and Mac using Continuity - Connect

SMS Relay - Set up and use –Yosemite/ iOS 8

SMS Relay - Set up and use –Yosemite/ iOS 8 (2)

Text messages forwarding

Messages – Fix Syncing Between Mac and IOS

Messages – Fix Syncing Between Mac and IOS (2)

Are you able to use FaceTime/iMessage on another device?