I had the same issue.
It should be resolvable pretty easily.
1. Make sure USB debugging is enabled on your phone. It's in the developer settings, which have to be activated, and this is different for many android versions. You can do a google-check on how to do this.
2. I think Mass Media Transfer has to be on as well, another transfer setting on your phone.
3. Did you install the google USB drivers? They are included with the Android SDK and need to be ticked on in the installer.
4. You can navigate to the android SDK folder with the adb executable in a command window, and run the "adb devices" command to see all connected Android devices. Esenthel will check this too, but only after compiling, so this is faster to check.
5. If no device shows up, it's most likely a USB driver issue. I had the exact same issue and managed to solve it by installing a universal USB driver, made by some saint. Here is the link:
https://plus.google.com/1035839393203262...Q5iYJEaaEH
6. Now, run the adb devices command again to see if anything shows up. If it does show up, but doesn't work in Esenthel, try launching in admin mode.
Hope that helps!