Why Vobot cannot find my device when I ask it directly?

The command of "find devices" or "discover smart device" only applies to Amazon Echo series because so far there is no API for Vobot to have this feature. However, you may use "Smart Home" or "Skills" sections in Alexa App to configure the device by simply signing in with a third party smart home device account.

As a third party device, Vobot can control or query any device that has already been setup and bound with Alexa.

As far as we know, the discover or control path is "Amazon Echo/Google Home" >> ha-bridge >> Device to control (Philips hue).

There must be some code running inside Amazon Echo/Google Home, to make it possible to discover the Node-Red or HA-Bridge, and then take control these devices. We also read this from https://github.com/bwssytems/ha-bridge:
ATTENTION: This requires a physical Amazon Echo, Dot or Tap and does not work with prototype devices built using the Alexa Voice Service e.g. Amazon's Alexa AVS Sample App and Sam Machin's AlexaPi. The AVS version does not have any capability for Hue Bridge discovery!

And we did a research, when asking 'find device", the Alexa voice server simply returns a mp3 saying "unable to find xxx". No further directive is given. So it's not possible to trigger the discover by voice, at least.

Although we think it's possible to trigger it on Vobot's App, as long as we find out that how HA-bridge can be discovered over the WiFi/LAN. It's still uncertain how we can add the device to Alexa's smart home device group. As far as we know there is no API for Vobot to handle linking the device or account yet.

We will push Amazon guys hard on this issue.

PS: to control your smart home device using Vobot, please visit this link: https://www.imore.com/how-control-your-lights-amazon-echo