Hi KittyRO
Thank you for contacting Microsoft Q&A Forum.
Based on your description, it seems that after reinstalling the authenticator application, you accidentally chose to start normally and activated the cloud backup instead of restoring from the cloud. Unfortunately, this has resulted in the loss of your previous backup account.
We regret that you will not be able to restore your account if you have lost the backup account. We're truly sorry that we’re unable to assist more if you are unable to recover or restore your Authenticator's account credentials because you cannot access your backup account.
Furthermore, please be aware that if you can restore your authenticator account, you will only recover the list of accounts, not the MFA for each one. To restore MFA for individual accounts, you will need to contact each organization's IT department (who has the Global Administrator right) so that they reset the MFA, allowing you to re-register MFA again by following this article: https://learn.microsoft.com/en-us/entra/identity/authentication/howto-mfa-userdevicesettings#manage-user-authentication-options
If you need further assistance or have any other questions, please feel free to ask.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.