A few things!
Are you having any trouble with your internet connection? Please make sure your connection is good, restart the mySugr app, and try again.
Another possibility is trying to use the same email address for both mySugr Logbook and mySugr Junior. They need separate and unique email addresses for registration.
If you use Gmail, there is a special trick you can use. Put a plus sign and some string of text (e.g. “+junior”) before the @ in your email address (e.g. email@example.com). This will make mySugr treat the email as new and different, but Gmail treat it as the same. You’ll even get the notifications from mySugr junior to your email-address. Is that nice or what?
If you already have a mySugr junior account and can’t login please send a message with the email-address you are using for junior and a short message (such as what error message you’re getting) to firstname.lastname@example.org – we’ll take a look at what’s going on.