RAK831 does not bootup - read this advice first!
I recently received a RAK831, which came pre assembled with a micro SD card pre installed with Raspbian. However I could not get the unit to boot. I checked the microSD card, disassembled the RAK unit to check the Raspberry Pi was OK, etc, etc. Nothing worked.
To save other users from a lot of wasted time. If you are having problems getting the unit to boot up. Do yourself a favour and throw away the USB cable that came with the RAK unit.
Use another cable you are sure works.
I am really unhappy that RAK have shipped the 831 with such a poor USB cable that will not even support the Raspberry Pi requirements! However, most people with have spare USB cables.
I am very sorry to hear this news, we will check later we shipped accessories available.