I too am having the same problem, I have been trying for the last two days to get PayPal Website Payments Pro to work but keep getting invalid vendor id. I have ssl and have installed both the PayPal Website Payments Pro module and paypal express modules. I have entered my user, vendor id, partner and password exactly as they appear in my paypal account. When i activate it not only do i get the vendor id error but express no longer works. I spoke to paypal on the phone but they say my credentials are correct! I am using zen cart 1.39a. I reset the express Paypal mode to Paypal and not Paypal-UK so that express checkout can work again but no joy with PayPal Website Payments Pro. I would like to hear from anyone who has a paypal uk account and has got PayPal Website Payments Pro working please

Regards

Bill