Seems like maybe your zwave radio is offline or something.
Try these ones:
/hub/zwave/healthStatus
/hub/zwaveDetails/json
Might give a better idea.
Also FULL results of http://YOUR.HUB.IP/hub/zwaveVersion I think if the radio is down it will either not work or not look correct. Should be a JSON string.
That's the one I said to check 3 times prior and you stated it was showing 7.15, I am guessing that was the SDK version endpoint from the other instructions.
The zwaveVersion output is like this: VersionReport(zWaveLibraryType:7, zWaveProtocolVersion:7, zWaveProtocolSubVersion:18, firmware0Version:7, firmware0SubVersion:18, hardwareVersion:1, firmwareTargets:1, targetVersions:[[target:1, version:7, subVersion:18]])
When that endpoint says it is not found, it is a telltale sign of a dead z-wave radio.