I'm trying to test Paypal Express Checkout with a sandbox seller account, and with sandbox mode enabled on the Magento Configuration.
The "checkout with paypal" button shows up on shopping cart but when I click it it redirects me to an URL like:
https://www.paypal.com/cgi-bin/webscr?cmd=_flow&SESSION=
And shows the following error:
Your session has ended
This transaction has expired....
According to this post, for sandbox mode I should be being redirected to something like:
https://www.sandbox.paypal.com/webscr?cmd=_express-checkout&useraction=commit&token=
When I copied the token and used such URL it worked fine.
What can I do to get the sandbox URL to be used when in sandbox mode?