How To Debug js code in the board?

Just tried "Latest build here",

• got a selectbox (first time, I saw this box)
  
• selected 1.3/1.4
  
• reset the board
  
• started flashing
  
• after some seconds got "Can't find STM32 Bootloader"
  
  

Checked flashing with a V1.80 and that runs fine.
Tried with your link again and got an error.
Do I have the wrong board for this build (it's from 1st kickstarter) ?