The Pretzelboard (NanoESP) needs a driver for the USB-to-Serial Chip CH340G to work properly. You can download the driver here:

Windows (Windows 98 - Windows 10, 32-Bit/64-Bit)

Linux Version

Mac Version (Attention: There seems to be a problem with MAC OS Sierra. Bellow are two links with walkthroughs:
https://github.com/jimaobian/CH34x_Install_V1.3/blob/master/CH34x_Install_V1.3.zip
https://github.com/adrianmihalko/ch340g-ch34g-ch34x-mac-os-x-driver )

Android Version

There is a Setup.exe file (Windows Version) in the Zip-Folder which needs to be executed. Choose Install in the following Window.

Die Installation
Die Installation

After a short time a message confirm the successful installation. Now you can plug in your Board und the driver will be chosen automatically.