Gamin Edge 520

Gamin Edge 520

I am hopping that someone can help me as I am having a lot of trouble with Gamin Edge 520 .
it records the rides ok when I go out ridding but when  I plug in the wire to the back of it and the other end of it into the usb port on the computer 
so that I can send the data to Stava to show my friends (encourage each other)
Garmin Express asks for my email address & password both of which I enter only to be told the password is wrong!
so I click on the forgotten password and am send a temporary password so that I can mark a new one,
all is fine until the next time I want to  send the data to Stava.
 
please can someone help me-Ian