I had the same issues. They told someone else here that you now had to use the VIP activation which was a lot of rubbish. This also didn't work for me. Good security,  I couldn't even use my account if the key was activated. I had to deactivate the key, purchase, then activate the key again. Like I said to paypal that's not what is suppose to work.

Eventually I spoke to one of the techs, I had to send them a few error logs and they got it sorted. It's been working fine since.

Try this,it worked for me.....

Log into the checkout screen using your password and your security code eg: password538124

Your password with the keycode will get you right through to the paypal payment choice page

This does work as I had the same problem for weeks and this solved it

Good luck