If you use SmartStart you just scan the QR code and wait little bit, they will pair. If they are not pairing it is possible they are out of range and/or weak signal.
DO NOT scan the QR code and then try to manually pair, you will have two processes trying to fight each other when pairing.
I recommend using SmartStart, once you understand how it works it is nice and easy.
See my SmartStart tips here: [APP] SmartStart Manager for Z-Wave (Long Range support) - #2 by jtp10181
Here are official docs on Zwave Pairing, it covers traditional and SmartStart: Z-Wave Manual | Hubitat Documentation
ALSO, after your struggles you should probably check your Zwave details page for "ghost" nodes and try to remove them before you continue. Read section 1 here: How To Remove Ghost Devices using hub tools or a UZB Stick
