I use versiono 4.5.3428. I use Chrome (IE as check). Settings is config are by the book. My Paypal account is set correctly.
Still payment (checkout) does not work :-/
Furthermore there are issues like:
Payment emailed: no e-mails are sent; download appears as an option :-/
Payment immediate: again the download option appears (it always appears not matter what user settings are set).
Add to basket works but checkout doesn't!
I'm getting a bit restless to see that no solutions are getting posted here ...