I got it working with Paypal. I tested it on the Paypal sandbox, got to the successful payment page on Paypal. When I click on the Return to Store button. It just keep loading and never leave the Paypal page and seem to freeze there. Then, I can no longer access my site with this same browser session (even if I open a new tab). I have to close the browser altogether and open it back again in order to access my Silverstripe site.
I'd appreciate if anyone can tell me how I can fix this.
Thanks!