iPhone 11 will not pair with my iPad

What, specifically, are you attempting to achieve by pairing an iPhone and iPad - presumably over a Bluetooth connection?

Whilst it is technically possible to do so, for the majority of applications, Bluetooth pairing of an iPad and iPhone is entirely pointless. If your intention is to use Cellular Hotspot features of your iPhone, this link is optimally achieved using the native WiFi hotspot connection - this being a largely automated process. Hotspot connections over WiFi offer substantially greater throughput, range and reliability.

How to set up a Personal Hotspot on your iPhone or iPad – Apple Support

If you still wish to pair your iPad and iPhone over Bluetooth, you first need to manually enable the hotspot feature on your iPhone:

Settings > Mobile Data > Personal Hotspot > Allow Others to Join - set to ON

Next, Bluetooth for both the iPad and iPhone must be placed in Discovery mode:

Settings > Bluetooth (accessing this page will automatically place the device in Discovery mode)

Whilst both iPad and iPhone are in Discovery mode, you can mutually pair the devices.

Again, I must stress, unless you have an unusual “edge case”, pairing of iPad and iPhone over Bluetooth is neither recommended nor necessary.

All of a sudden my iPhone says my ipad is unsupported. The reason I liked them being paired is if I were on my ipad and received a phone call, I could answer it on my ipad. Is this not a good thing to do. My iPhone is two years old and ipad is less than a year old.

Trying to sync messages & contacts via private WiFi. Any anwers on that?