Please enter your email address into this page and it will (re-)send your certificate.
Once that arrives in your inbox (usually within a minute or so), install that into the licence manager and it should work from there.
My guess is that you were still using an evaluation licence without installing the purchased certificate yet, since purchased certificates don't expire.
If you still have problems, please email our sales contact address with your purchase details and they can look into where things are going wrong. (But please don't post any purchase details here to the forum, since anyone can see them.)