The thing is, the block’s template file must be registered somewhere, either in a plugin, a mu-plugin, or somewhere inside your theme, but without being able to look at the files directly it’s going to take an eternity to track down.
Honestly, without a closer look this is getting complicated to debug remotely.
would you like a login?
Please don’t post any logins here. If you can, the safest way is to create a staging/clone of your site and send those details instead. To keep things extra secure, you can put the login info into OneTimeSecret and send me the link in a private message
Indeed, I’m mostly just curious why it would work if he creates an exact copy of the page and not on the home page.