Well it is possible that your other accounts are not showing up in the Microsoft Authenticator App (MAA) after reinstalling it on your Android phone due to the MAA might not have been backed up before you reinstalled the app, causing the accounts to be lost. If you didn't enable backup during the initial setup, the accounts won't be restored automatically.
Also consider The MAA supports various types of accounts, including personal Microsoft accounts and work/school accounts. Ensure that you're using the correct type for each account.
To get your other accounts back in the authenticator make sure that you have a backup of your accounts from the previous installation. If you didn't have a backup, you'll need to re-add the accounts manually to the MAA. For each account, you might need to go through the setup process again, usually involving scanning a QR code or entering a code provided by the service you're securing with 2FA.
Remember to enable the backup feature in the MAA for future cases to avoid losing your accounts again.