DPD uses payment amount verification instead of button encryption to protect your downloads. Your PayPal account may be set to only accept encrypted payment button requests from using other systems. Turning off this feature will allow DPD purchases to work alongside your encrypted buttons.
Encrypted buttons are not required because DPD adds additional verification to the checkout to prevent fraud.
PayPal users with the new "sidebar" style profile:
Please see Step 1 of our PayPal Account Setup & Troubleshooting Guide.
PayPal users with the "classic" profile:
Please see Step 1 of our PayPal Account Setup & Troubleshooting Guide for the PayPal classic profile.