YITH Problem with PayPal

When the subscription plugin is enabled, PayPal will not work.
I am using the PayPal Sandbox for testing.
If I disable the YITH subscription plugin, PayPal works properly.

The error when going to PayPal from my site is:

“PayPal
Things don’t appear to be working at the moment. Please try again later.
Return to Merchant”

I’d send a screenshot if that were possible.

Again, disabling the YITH plugin allows PayPal to work as it should.

The page I need help with: [log in to see the link]