X Theme Integrity 404 error Oops! You blew up the Internet

I need to change the error message for page not found to something other than “Oops! You blew up the internet.” I’ve looked at old forums and have seen answers from 2014 and 2016, but cannot find anything I can work with because _LANDMARK-HEADER.PHP doesn’t seem to exist in my current installation.

Can anyone please tell me how to change the words in the header and body of the 404 error page?

Hello,

I’m sure the author of that theme would know where to make the edit. Here is their support information - https://themeforest.net/item/x-the-theme/5871901/support

Thanks!