[Pro Sites] Redirected payment gateway paypal can't login

Hi,
I tried to make a payment through the provided paypal link. It brings me to the paypal login page (IINM, sandbox.paypal.com) , I'm not able to login with my account.
I got curious and opened another browser and tried to login through paypal.com and it works.
This means that there might be something wrong/outdated with paypal's login from the redirected payment gateway.