Neither Happyforms nor Contact form 7 send from the contact page - but work else

That's fine, yes

I tried adding a new page called test with the happy form shortcode, after publishing, there's a server error:
https://www.screencast.com/t/WX2jWfSvITB

I can't view the page. Let me know the test result if you can view it.

Found the form works in preview mode, as long as it's published, it stopped working.

I suspect it's a server-related issue.

Could you try to activate twenty twenty one theme to test?

Let me know!

No luck, unfortunately...I even tried messing with server settings, but nothing works

Unfortunately we are out of ideas here.

If the issue also exists in a Twenty series Wp theme then it's definitely not a theme related issue.

I'd recommend checking with the form plugins' support team and see if they can offer some advice.

Sorry about that!

So I found a change in the settings that will allow the forms to work, but I'm confused as to why -

If i change the permalink structure to "plain" as opposed to "post name", the forms seem to work. But, then the url naming scheme is odd. Any idea how to address this?

Unfortuantely I'm not sure why that would be the case.

I'd recommend checking with the forms support team to see if they have an idea :)