How do I 'register' my email on Android?

[Charlie Darwin]

Have "Aston Thunder" running Android 5.1; error message appears frequently "Unregistered email" when trying to run some apps/extensions [eg 'Line' free calling] & the app won't open.
Have tried to register my email [which works fine in Gmail] but Catch-22 happens. In order to Register I must first log on which I can't due to the 'unregistered email' !

Been round in circles for hours trying to solve this weird behaviour but cannot 'Register' & LINE will not run.

 

[B. Diddy]

Did you install Line from the Play Store? Try going to Settings>Apps, select Line, and Clear Cache/Clear Data. Then open it again, and select the Register or Sign Up option.

 

[Charlie Darwin]

Thanks, BD
In fact it occurred to me that getting a second sim from a different carrier, making a complete fresh start might help; also when one sim runs out of cash I could switch to the other & top up later. Surprise- everything works on sim2! LINE is FINE!
I don't recall where I got LINE from but I try to avoid 3rd party sites cos you don't know what junk they may include with the download?