processing error. v.1.2.16 FastCheckout Error: Unexpected error has occurred.

[kiwi]

Hi There,
Hoping someone can help with this error a customer received while trying to process there order online the customer said,
> processing error... what does this mean. I am trying to confirm my order<

I haven't heard of this before, I checked the Log and found what might be the issue below.

The PROBLEM IS I CAN SEE THE POTENTIAL PROBLEM BELOW, BUT I DONT KNOW HOW TO REMEDY IT :-( looks like I need to fix the order database so it can be built on.
can anyone explain in layman's terms, how I can FIX this?

I can checkout with no problem, could it be at the customer's end??

2021-03-31 0:24:10 - App Error: AbanteCart core v.1.2.16 FastCheckout Error: Unexpected error has occurred. Unable to build order data based on array: array (
'session_mode' => '',
'LAST_ACTIVITY' => 1617150250,
'fast_checkout' =>
array (
'' =>
array (
'cart' =>
array (
),
),
),
'language' => 'en',
'country_id' => 153,
'zone_id' => 2344,
'customer_group_id' => '1',
'cart' =>
array (
),
'currency' => 'NZD',
'fast-checkout' => true,
)
Trace:
#0 /home/kiwicust/public_html/extensions/fast_checkout/storefront/controller/responses/checkout/pay.php on line 1743
#1 /home/kiwicust/public_html/extensions/fast_checkout/storefront/controller/responses/checkout/pay.php on line 384
#2 /home/kiwicust/public_html/extensions/fast_checkout/storefront/controller/responses/checkout/pay.php on line 340
#3 /home/kiwicust/public_html/core/engine/dispatcher.php on line 293
#4 /home/kiwicust/public_html/core/engine/response.php on line 80

[timlight10]

Do you have Guest Checkout turned OFF? I ran into this problem when Guest Checkout was OFF.

[kiwi]

Guest checkout is ON
Worth a try. hope it is an easy fix.
Thanks