I have a site that is currently running CartThrob v2.7 and using "Paypal Website Payments Pro" for the gateway. I need to make some updates to the checkout process, and tried switching the gateway to "Sandbox" mode. However, when I do that and try checking out, I get a "SSL connect error (35)" error.
The checkout process works when the gateway is in "Live" mode (but obviously, that won't work for development.)
AFAIK, all of CartThrob's PayPal credentials are correct and up-to-date, and the PayPal account is in good standing. I know that "Paypal Website Payments Pro" is a legacy product, but switching to another gateway is not currently an option.