Q: FaceTime won't allow sign in

Do a backup.

Quit the application.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J.  When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder.  Select Library. Then go to Preferences/com.apple.FaceTime.plist. Move the .plist to your desktop.

Restart, open the application and test. If it works okay, delete the plist from the desktop.

If the application is the same, return the .plist to where you got it from, overwriting the newer one.

Thanks to leonie for some information contained in this.

If the FaceTime window opens with a white camera icon with a slash through it on a black background, that means it can't find a camera. Without a camera, it won't work. Follow the instructions in this support article.

Otherwise, I suggest you take each of the following steps that you haven't already tried, stopping when the problem is resolved. Back up all data before making any changes.

Step 1

If the FaceTime window shows that it's turned off, turn it on.

Step 2

Launch the Messages application and sign in to your iMessage account. If you get an error message, stop here and post the complete, verbatim text of the message.

Step 3

Make sure you know the ID and password you use with iMessage. Launch the Keychain Access application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Keychain Access in the icon grid.

Use the search box in the toolbar of the Keychain Access window to find and delete all items with "iMessage," "FaceTime," or "Apple Persistent" in the name. Log out and log back in.

Step 4

Hold down the option key and select

          Go ▹ Library

from the Finder menu bar. Move the following items from the Library folder to the Trash (some may not exist):

          Caches/com.apple.Messages

          Caches/com.apple.imfoundation.IMRemoteURLConnectionAgent

          Containers/com.apple.FaceTime

Leave the Library folder open. Log out and log back in. Try FaceTime again. If it works now, stop here. Close the Library folder.

Step 5

In the Preferences subfolder of the Library folder, there may be several files having names that begin with any of the following strings:

          com.apple.FaceTime

          com.apple.facetime

          com.apple.ids

          com.apple.imdsmsrecordstore

          com.apple.imessage

          com.apple.imservice

Move them all to the Desktop. There may also be a file with the name "com.apple.imagent.plist". Move that to the Trash.

Also in the Preferences folder, there's a subfolder named "ByHost". Open it and do the same thing.

Log out and log back in. Test again. If FaceTime now works, you may optionally be able to put back some of the files you moved to the Desktop in this step. Relaunch and test after each one. Eventually you should find one that causes FaceTime to malfunction. Delete those files and recreate whatever settings they contained.

If the issue is still not resolved, quit FaceTime and put all the items you moved to the Desktop back where they were. You don’t need to replace the items you moved to the Trash.

If you get through all the above steps without a resolution, post your results.

for me , same probleme to login :

Votre identifiant Apple « v*****@gmail.com » ne peut pas être utilisé pour configurer FaceTime à l’heure actuelle.

S’il s’agit d’un nouvel identifiant Apple, il est inutile d’en créer un autre. Pour utiliser cet identifiant Apple avec FaceTime, contactez l’assistance de l’app FaceTime avec le code ci-dessous.

Code client : 3324-6064-2510

thx to reply