Password isn't Working for Mobile App/ Not able to log into the mobile app/ Unable to log in on my phone but my username and password work on my PC.

It's important to note that the mobile app does not need a password, it needs an auth code instead.
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An auth code is used on the mobile app, while a password is used on the web app (in addition to a username, which can be different than your email).

When you are invited to the app, or assigned access to an event for the first time, your authentication code is emailed to you. If you have lost your authentication code, you can reset it from the login screen, or your Captello admin can re-send it to you.