Then it might just be that your router isn’t able to see your iPad’s hostname. Local hostnames sometimes just choose not to work on mobile devices. I’ve had Android devices where the hostname didn’t work and then started to, and have heard of others experiencing the exact opposite. I thought that iOS is better about that, but it could be more to do with the router.
That’s why I use static IPs–I never have to worry about how devices are identifying themselves. If you go that route, note that newer iOS devices specify virtual MAC addresses that are specific to each wifi.