Session lost after redirection

Hi, 

I am using the latest version 3.9.1 of Eshop and I have the following problem. When the customer is at the checkout and redirected to a payment gateway (PayPal or Credit Card), then the session is lost after returning to the eshop. So for example if he clicks 'cancel and return' then his cart goes empty and if he was logged in, he is logged out after the return. The issue occurs whether the customer has a successful payment or clicks the cancel and return link.

Could you please think if there is any configuration or reason why this is happening?

Thanks

I think I found it.
It was the difference between www and non www in the website address. It has to be the same everywhere.
The website should work with only one of these two cases, not both, and any redirection from a payment method should use also the same choice as the website.

Hello,

Yes, that's it.

Sincerely, Giang