Only For Guest Checkout: 'Error Updating Cart. Page not found.'

[smusselm]

I just found out today that guest checkout isn't working. When you check the 'Terms of Service' Box, you get a pop up that says 'Error Updating Cart'. When you close out of that you get one that says 'Page not Found'. When logged in, however, everything works beautifully like it should.

I've unchecked the Ajax for OPC option and it only redirects to a 404 page.

I've explored jquery issues and setting various things in jquery easy. I've turned off other modules that use jquery. No avail.

I looked into my security component about same origin access.

The only lead I have is a console error: HTTP404: NOT FOUND - The server has not found anything matching the requested URI (Uniform Resource Identifier). (XHR)POST - https://...../cart?tmpl=component

Not sure where to look, or try.  I remember this working before we went live. Not sure if it's related to the HTTS certificate that for networking reasons had to be applied after the golive. 

Please help!

[GJC Web Design]

live url?
versions?

[smusselm]

Live URL: [Removed]

VM Version: VirtueMart 3.6.10 10211
Joomla Version: Joomla! 3.9.16 Stable
PHP Version: 7.2.17

I am also getting another 404 error when attempting to 'log out' from the account page.

[Jörgen]

How is payment method arranged ?
Try without sef.
Menu item for cart ?
Menu item for user pages ?

Jörgen @ Kreativ Fotografi

[smusselm]

You guys nailed it!  Thanks!

In all the crazy customization I did, I forgot to set up a menu item for the cart.  Joomla didn't know how to route it.

[Jörgen]

Nice to hear that it works now.
Jörgen