Hi Elainenfinn,
Thanks for coming out to Apple Support Communities for help signing into iMessages and FaceTime. We want you to be able to easily use each service from your iPad, so we're certainly glad to look into this with you and help.
So that we're on the same page, what's the version of iPadOS installed on your iPad Air 2? This can be found under Settings > General > About.
Have you had a chance to restart your iPad and join a different Wi-Fi network since noticing this error message during the activation attempt? If not, let us know if you'll be able to do so, and if it helps.
If the issue persists, we've got a great troubleshooting resource to share with you:
If you get an error when trying to activate iMessage or FaceTime
Let us know if you've got any questions about this guide, or if you find that the issue persists.
Have a great day!