Hi @Cochran, Joel ,
I couldn't reproduce this issue on my SharePoint Android APP. As per my test, When a user visits the page for the first time, he will be asked to sign in with MFA. He can access the PowerApps App after completing the authentication(in my case, I will receive a text message on my mobile phone and I just need to type the verification code in the message into the SharePoint APP).
Make sure the owner of the PowerApps APP has shared the APP to those MFA users and the users has been assigned proper license to access the PowerApps APP.
If an Answer is helpful, please click "Accept Answer" and upvote it.
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.