Clicking on Paypal button quickly opens/closes external paypal window but nothing happens

Problem

When you enable Paypal within the Commerce Braintree module and then follow through the process of ordering an item, at the last step if you select paypal, you can enter your billing address and then click on the Paypal button. Then an external Paypal window quickly opens and closes automatically and nothing happens after that. I cannot proceed with the order at this point. Repeatedly clicking on the Paypal button has the same result each time.

I am setting this to critical as Paypal basically does not work. I tested this on 2 different servers and got the same result. I thought it was because commerce braintree was using an older SDK so I applied the patch at #3161031: Upgrade to the latest Braintree SDK (3.63.0) → and I got the same result.

Steps to Reproduce

Install this module (latest 8.x), enable paypal as a payment option and try to order an item and pay with Paypal.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes