Contact form not working when dragging page to another site

I don’t have Classic. I’m using 8.9.4 still. My business is not doing well, so I really don’t want to spend the upgrade to Classic right now. My problem is with the contact form. I have multiple sites that are almost identical, so I can use the same contact form on all of my sites. My one site’s contact form is working fine, when I drag the working page contact form into the site that for some reason is not working, it no longer works with the other site, even though I didn’t change anything. I’m not getting error messages when sending. It looks like it’s seeding fine, but isn’t. I’ve always had problems with the contact form working then not working. Any ideas of what is going on?

As a first step I’d recommend making sure the page is set with a .php extension.

I have the filename: indexj.php
Is this what you mean? Sorry I’m kind of green on these things, even though I’ve been using RW for my sites for over 13 years.

Yes, that’s correct.

All the settings should be identical with the page from the other project I’m dragging and dropping it from, since it’s just a copy of the same contact form page. I don’t get it?