During the check out there are 2 payment methods: DIRECT TRANSFER and Paypal.

DIRECT TRANSFER is where you need to log in to your bank account and transfer your grocery shop manually.
PayPal is where you want to pay via Credit Card. You don’t have to have Paypal Account in order to use this option.
Paypal is a trusted third-party chosen by Tozerba to ensure that the payment is secured and protected.

If you choose the payment via DIRECT TRANSFER, you will see below screenshot:

Question: “Every time I want to pay my grocery, I keep receiving error message – Your Session is Expired, why?”

Answer: Again, once you have submitted the order and choose DIRECT TRANSFER, system will send invoice to your email.
You need to login to your bank account and transfer the grocery shop invoice manually.
This error message is telling you that you couldn’t see your previous list of grocery because your previous order has been completed.