Clicking the 'confirm whitelisting' button in the dashboard just makes sure the site is routed through that smaller set of IPs - it doesn't actually effect any changes to your hosting / firewall setup.
Being on shared hosting can mean that the correct whitelisting is not available for your site - often, hosts won't be willing to whitelist a subset of IPs (like Ezoic's) for one site since it would end up effecting many other sites on the same server --- which is what the host response seems to be suggesting.
It might be worth looking to upgrade to a VPS or dedicated server to avoid these types of issues, or to change to a known compatible hosting setup: https://www.ezoic.com/certified-seamless-with-ezoic/