My website was pointing to a strange IP address

That IP address is a premium hosting IP address. If your website has been migrated to premium hosting, then that’s expected behavior.

The notice warns you that your domain is not setup correctly for your InfinityFree free hosting account. But since you’re using premium hosting, that’s exactly what you want, you don’t want to pay for premium hosting and then use free hosting.

That said, since you have a custom domain name and are using premium hosting, I recommend that you point your domain name to the nameservers of your premium hosting account instead. That way do you get all premium hosting features on your domain (like full DNS management). After a few days, you can then remove the domain name from your free hosting account with us, to prevent similar confusion in the future.