Checkout suddenly stopped working

-- url of the page with the problem -- : www.beeswaxcandleshop.com/store/beeswax-...ax-tapers-pairs.html
-- HikaShop version -- : 5.0.0
-- Joomla version -- : 4.3.4
-- Error-message(debug-mod must be tuned on) -- : We are sorry!
Gantry 5 provides a custom error page for you to configure with either positions, particles or a combination of both, as well as styling.
www.beeswaxcandleshop.com/cart.html

Suddenly my checkout and shopPing cart no longer work - all I remember doing is adding new coupon and also looking for the word guest in the languages area. the page goes to a 404 type error page - turned debug on - but did not help -Store display works fine but no checkout ---BIG PROBLEM - HELP

This is what I think may be happening - a few days ago I was trying out using login on our site. It did not workout and you recommended not using it - good solution. "hika- problematic" is an image of the set up

A few days later I noticed a problem with the check out. Something was doing something to my browsers - I tried firefox, chrome and edge. Clearing cache on site, server and browser made it work again.
"hika-working" image is the setup I have now -seems ok except:


When I try a new order using email This email address is being protected from spambots. You need JavaScript enabled to view it. (my email and superuser email) I get the "hika-login-2" error


I use another email address, everything works. I have login set to "no" but it acts like it is still there. Is this the issue?

Other things that could interfere:
I am using PHP version, 8.0.30 - old - whenever I try to upgrade, the site breaks - I think I have issues left over from my old joomla3 install - I am working on cleaning it up but still cannot upgrade php yet. (any hints)