Hello,

Actually, by default you see the Theme’s default 404 Page on the Site, something like this: https://ibb.co/TbsTTvJ

So, if you want to have a Custom 404 page then you need to go to Dashboard > Pages > there create a Custom 404 Page > and then go to Dashboard > Theme Settings > Other > Custom 404 page > there select your newly created Custom 404 Page: https://ibb.co/T1ZXxQS

Best Regards