Oh, but it should work. Please check your browser Console for an JavaScript error message or alike that looks being thrown by a braintree script file (it could be a script within the plugin itself or even the Braintree JS SDK).
Nevertheless make sure the integration JavaScript loads. Open the checkout page, View Source, lookup a line that contains woo-mynix-braintree-gateway-paypal.js. If there is no such line then for some reasons it wasn’t loaded so the PayPal integration won’t work.
If nothing above verifies then just make sure that:
because in such cases it is the Braintree script that won’t initialize the PayPal button for the mentioned reasons.
Please let me know if you found anything mentioned above.