Why does my checkout button lead to a 404 error page?

I am beyond frustrated with Shopify. After a solid month of trying to fix problem after problem on my Wordpress that’s connected to my Shopify, I’m down to what I pray is the final major issue. When the Checkout button is pressed, I get a page that says,

“Oops! Page not found 404”. On the Shopify side when I try to fix checkout issues it says, “This content is blocked. Contact the site owner to fix the issue.”

That message is up for about half a second and then is replaced by the message,

“Failed to load the page. This page is not compatible with the editor due to one of the following issues: * Page is redirecting to an unsupported URL * Page failed to load due to an error.” and then gives me the options of “View Documentation” or “Try Again”. (And that’s only on the few times the page will actually load to give me these messages.)

I’ve followed every tutorial I could find. I’ve fixed every section of Shopify and Wordpress I could find to fix. I’m ready to ditch Shopify completely since it hasn’t worked for the whole year I’ve been paying for it. Can someone PLEASE help me??? I finally found a Shopify page that said to contact them if the instructions on the page didn’t fix the problem but it was a joke because when I clicked it there was zero Shopify contact information, as usual. Shopify is killing my business. PLEASE someone help me! TIA!

I have zero intention of maintaining a Shopify store after I was finally
able to chat with someone. This is the worst platform with the absolute
worst “customer service”. I’m not sure how they’ve stayed in business.
Also, I’ve had sales- just not on Shopify because I could never get the
cart or checkout to work and Shopify is clearly uninterested in helping
customers.