Customer redirected to empty cart after order confirmation

[Jurist]

Hello,

I have been developing multiple stores with PS 1.6 selling to multiple countries. I have no problems with the stores but with one selling to Germany. Server information on attachment.

This is a single order with the problem (2 errors Frontcontroller::init - Cart cannot be loaded or an order has already been placed using this cart).

The problem is:

The customer after adding a product to shopping cart, registering and paying is redirected to empty cart page. There's no order confirmation and order is created in back office but without status.

I have found a lot of topics describing similar issue, but people were reporting problems with being redirected to an empty cart after adding a product. Looks like adding a product works well, however the problem with failed orders created is really severe.

What is also strange is that it happens to only 10% of customers. Others are able to create orders without any issues, we have also been unable to replicate the problem ourselves. Obviously 100% customers must be able to pay. We have been trying to find what in common have those people unable to pay, hard to see anything, there are some tracks that it may happen because of firefox browser.

We use 5 step checkout and payment is PayPal Plus module, purchased from Prestashop marketplace (the issue may come from the module, however developer tested 20 orders with development store version and he says that he didn't find any problems). When we were testing the store ourselves with sandbox and live accounts orders went through successfully without any problems.

The things I have done so far:

• - cleaning DB (ps_connections, ps_connections_page, ps_connections_source) (link)
• - changing ps_cart auto_increment (link)
• - geotargeting is turned off, setting localization from browser turned off
• - there are no any javascript errors,
• - eBay module is not installed (link)
• - shop is not in multistore module, stock_available table has proper quantities and there are no obsolete redundant rows,
• -  Core/Business/Stock/Core_Business_Stock_StockManager.php at line 126 issue was fixed (link),
• - can't see any errros in apache error_log,
• - I have made override for PaymentModule.php (link)
• - I have made override that changed cookie name (link)

The problem persists. We are losing sales. The problem is present on the PS forums, however none of the solutions helped me. After paying customer is redirected back to our website like he's never been on it before, cart is empty, because he's not recognised as a customer who just paid order isn't confirmed, he doesn't receive any emails, order is created in back office of the store, however without statuses. 

I would greatly appreciate any suggestions what else can be done in order to fix the problem.

Thanks

[Jurist]

Just tried another thing:

- changed store domain from non-www to www, somebody just ordered again and problem happened, there's an order without a status.

[Jurist]

There's another thing I tried, I changed ciphering algorithm from mcrypt to default (Blowfish).

Surprisingly, this option was hidden in back office (no idea why). I had to manually change db row PS_CIPHER_ALGORITHM to 0.

For now, there've been 20 orders and no issue, will write if that helped or not (and will continue to find the solution if possible) so hopefully this threat will help someone.

Cheers

[Jurist]

Okay, we have just received another order without a status, changing ciphering didn't help.

I am slowly getting out of ideas what is causing the problem. I would highly appreciate any tip of at least how could I debug this? I think it's a cookie issue, how do I track cookies in prestashop?

[Mar89]

@Jurist have you solved your problem? I have the same issue in my store from 2 weeks :<

[Jurist]

We moved to a different hosting and made major upgrade to Prestashop 1.7.

There was something I did which fixed the problem even in Prestashop 1.6 however I don't remember now what it was unfortunately :(