Why do our iDevices give a page not found error when trying to connect to profile manager website?
Have you verified that all required ports are open from the iPads to the server? (Port 1640 specifically, but also you'll want to ensure access to 80/443 for web and 2195/2196/5223 for push)


Lion Server: Ports used by Profile Manager


You can also run some tests to see if this is a problem with the server itself or with the network. Connecting to the server's IP address from the iOS device will rule out DNS and other issues.

I've found it helpful to open the Console app and watch /var/log/apache2/access_log for incoming requests so you can see which iOS devices are getting through to the server. That log shows you the IPv4 or IPv6 address of each connection request so you can detect which devices are networked correctly to send traffic to the server and narrow down in the chain where your problem lies.

Hopefully this helps others with DNS issues in getting to the same resolution as you.