For charging, please, connect the power charger to EEG Dev Kit and then to mains. Blue indicator shows charging and switches to green color, when charging finished (charging indication works if device doesn’t perform any other actions). Also, you can check the battery level in Device Details menu.
Full battery charging normally takes 2-3 hours.
Note, that EEG session and tES can’t be enabled whilst device is charging. This is both for safety and quality of recorded signal.