A Microsoft app for iOS and Android devices that enables authentication with two-factor verification, phone sign-in, and code generation
Thanks for your question. As per Microsoft Document, If you delete the authenticator app by mistake, there's no way to undo it. You'll have to add the authenticator app again, following the steps in the Set up the authenticator app section of this article. Also found similar thread https://answers.microsoft.com/en-us/msoffice/forum/all/accidentally-deleted-the-microsoft-authenticator/acfb9417-f06e-4e6e-93cf-6144f04b1c3d in case if that helps you. Thank you!