We figured out the problem in our OSCommerce Paypal module. We were passing duplicated variables. This may not be the problem for everyone but essentially we followed the "Payment Standard Upgrade FAQ" steps to debug. Passing currency symbols ("$", "£", etc.) or values other than integers (1, 2, 3, etc.) and decimal points (“.”) in the amount field. For example, "1234.50" is correct, but "$1,234.50" isn't allowed. Passing country code values greater than two letters. For example, "FR" is correct, but "France" or "fr_FR" isn't allowed. Passing more than 127 characters in the item_number field. For example, don't use the item_number field for "Note to Buyer" information. Passing more than 64 characters in the option fields (on0, on1, etc.). Passing duplicate empty parameters. Passing address_override=1 without passing an address. If you aren't aware of what variables you are passing, load up your site in Chrome and checkout until you get the blank Paypal screen. At that point right click the blank area and select "INSPECT", go to the "NETWORK" tab then press F5. You should see something like WebSCR. Click that link and then click the "HEADERS" tab. Find the POST VARIABLES area under Request headers and see if your variables are duplicated. Hope that helps! -Kevin
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