Select a supported synth, then flash its latest .kup package directly
from the browser.
After clicking on "Flash", your browser will ask you to select DFU device. If the list is empty, try fixing your USB drivers with Zadig. Mask1's screen and lights are turned off when it is ready to receive an update, this is normal. Do not exit this page or disconnect your device during the update. Do not switch focus with other tabs during the update.