Devices > Discover Devices > Z-Wave > Start Z-Wave Exclusion then go press the button on the Range Extender you should get a message saying unknown device excluded but might not. Then Start Z-Wave Inclusion. A countdown will show up. Go press the button on the range extender and come back to see that the hub found it. Sometimes it takes up to 45 seconds or so before it discovers it after you press the button.
What hub model do you have? If it is a C-7 there are some pairing/zwave issues right now.
You may want to just wait until the next hub firmware release. If you can't wait, try doing a gracefully shutdown (not reboot) and remove power for 30s.
Okay! I think this was the issue. I didn't think I was that far. Plugged them in and repeated the steps next to the hub and was able to install 2 range extender devices! THANKS!
Now I unplugged them and re-plugged them in away from the hub. How do I confirm they are working properly?
Give them some time to settle in to their new home. It can take a few hours for them to find out about neighbors. Run a z-wave repair and see that they are reporting correctly.