When you sign into Read&Write and then enter your Product Code to Activate, this then licences your email address to the product code on our system so you can get the full feature set. Occasionally it can take a few hours for the email address to licence on our server so if you close Read&Write and then reopen it straight after you enter the product code, it can sometimes ask you to activate again.
This is just a time delay on our server, just keep Read&Write open for a couple of hours after you activate and then when you close it and reopen it, Read&Write will stay activated.