DIAGNOSIS The battery is likely in a deep discharge state, or there's a poor connection at the charging port. Yeah, this one's common if it's been sitting in a drawer for months.
FIX Unplug the USB-C cable from both the blender and the wall adapter. Use a can of compressed air (or give it a sharp, dry blow) directly into the blender's USB-C port to clear any pocket lint. Reconnect everything firmly. Leave it plugged into a known-good wall adapter (not a computer port) for a solid 4 hours, even if the light is red. Sometimes it needs a long, slow trickle charge to wake up.
IF THAT DIDN'T WORK The charger or cable might be the problem. Try a different USB-C cable and a different 5V/2A (or higher) wall adapter. The blender is picky about weak power sources.
HEADS UP Don't try to use it while it's plugged in. The charging circuit and motor circuit are separate; it won't operate from wall power, and trying to force it can confuse the battery management system.