Purchase error: Your Transaction cannot be completed

I can’t buy the trial version, it says your transaction can’t be completed.
I’d like to test the premium version and another question, if I buy the premium version will it stay after I re install the software again?
How will it work I I reinstall the app.

It’s an error returned by the Google Play servers, it seems that it could be caused by various reasons.
Have you already tried the instructions from their help page?

There’s also some suggestions here.

Yes, as long as you use the same Google account on your phone.