Polylang clushing with another plugin

Hi,
I’ve been using Polylang for a while now and I’m very happy with the plugin.
I had to add another plugin to the website I’m working on that is essential for my clients payment method – its a plugin that I downloaded from the payment gateway website which is compatible with woocommerce. Everything works well but Polylang.
As soon as I turn Polylang “on” the plugin page refreshes and goes into a white screen and only by disabling Poly via FTP I can get back to the dashboard. I must say that the website at the front end works well with Poly “on” but not the “admin” side. Any advice what I can do so i can continue and use Poly for this website? Thanks!!