It was authenticating a few days ago. Now it isn’t, even for battle.net.
are you using the old stand alone mobile version? that was retired in Jan of this year. Players were to migrate to the Battle.net app which is where the authenticator is now located
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If you didn’t move over to the battle.net app, then yes. The old stand-alone app for the authenticator was retired (emails were sent about this) and anyone with the authenticator under the old app had theirs removed along with receiving instructions on setting it up under the battle.net app 
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