Just setting up our PayPal Express integration on WHMCS 5.1.2.
I've done this before on shopping carts and never had a problem, but for some reason I can't get WHMCS to complete any orders. The module is currently set in Test Mode (PayPal Sandbox) and I've entered the correct Sandbox API credentials into the WHMCS PayPal Express payment gateway configuration.
We can browse to a product, add it to the cart, specify server details, choose to pay with PayPal etc but when we get to the final part of checkout we never get past a screen that says "Please wait while you are redirected to the gateway you chose to make payment..." and has a couple of PayPal buttons on it (please see attached screenshot).
Does anyone have any ideas?