Since we now have a different credit card processor, you no longer need to use PayPal. If you are trying to use PayPal and are having difficulty, it's not really something we can control. That said, one possibility is that you have blocked pop-ups in your browser which can cause problems with PayPal. Please visit PayPal's help area for other possible solutions.
If nothing works, we can try sending you an invoice from within PayPal. That has worked in cases where nothing else would.