Unable to update Homepage – get 404

All of the sudden a few months ago I have not be able to update the Homepage – just the homepage. I am able to edit all other pages of my site and add new pages. When i try to make any minor change to my homepage, or preview changes, i get a 404 error…
https://totallifetimecareins.com/wp-admin/post.php

I’ve already tried:
-updating the permalinks
-deactivating my security plugin (WordFence) and trying to update
-checking my .htaccess file. I don’t have much experience making changes to this file, but based on other forums I have read the .htaccess file looks right and if i was unable to update my entire site I would be more inclined to think it was a .htaccess issue, but since it is literally just the homepage that I am unable to update makes me think the issue is something else.

I read on one post that i should disable mod_security and try to update, but I don’t have the option in my cPanel to do that. If that could be the cause of this, I will coordinate with my hosting provider to do that for me, but I wanted to check here first to see if I can try anything else.

I am on WP version 5.2.1 and I’m running the Broker theme 1.6.1

I have not tried changing my theme yet, mainly because i have never changed themes after all the design work i did and did not want to have to re-do all my pages. If i change themes would all my work in the Broker theme be lost?

I appreciate any help you can provide. I am at a wall with things to try to resolve this weird issue.

Thanks.

The page I need help with: [log in to see the link]