Why does the app goes back at the beginning when I open the SMS/Phone verification notification message while registering?

This can occur with some Android browsers.
There are two solutions:

1) when you are in the PRIOjet registration window where you enter your email/phone nr., please click on the 3 menu items in the top right corner in your mobile browser and open this registration page as “open in Chrome”, then the page with your entries will remain, even if you open your mail program on your cell phone.

2) As an alternative, you can use a web browser on a desktop or laptop and access the app through https://app.priojet.com. You may also want to use a Hotel PC or Desktop to register for the first time.