It’s a supported door lock (The zwave one) but not fully supported. You should be able to get it to lock and unlock remotely, but you may not have remote support for changing custom lock codes.
If you get in touch with email@example.com, they should be able to help you.
That said, issues with locks are almost always due to distance.
The first time you pair the lock, for security reasons, the hub has to be very very close to the lock. Typically about 6 inches. This is a requirement of the lock manufacturer, not SmartThings, to make sure the lock doesn’t get accidentally paired to the wrong controller.
After that, you can move the hub back to its usual position.
However, there can still be an issue with getting messages to and from the lock if you do not have a repeater that supports zwave “beaming” within about 15 feet of the lock.
When I first set up my doorlock I had problems similar to the ones you described. I was able to fix it just by swapping two plug-in modules in the room. One supported beaming and one did not. I needed to have the beaming one be the one closest to the door lock so that the messages would be held until the lock picked them up.
But again, support can help with all that.
Good luck! Mine worked very smoothly once I had the devices positioned appropriately.