We have php 7.1, WordPress 5.0.3, and easy appointments 2.3.12
We have installed the connector app and followed your instructions for installation and connection to PayPal. When we test it out, the PayPal box pops up for a moment and then disappears. it does not give any errors on the page. Here is a link to the page with the app on it: http://vinayaka.life/services/
I tried production mode and sandbox mode, nothing works. Any ideas?