DIAGNOSIS The battery isn't getting a charge, or the internal power circuit is stuck. This usually happens if the USB-C port is finicky or the battery got deeply drained.
FIX First, try a different charging setup. Use a standard 5V phone charger block (not a fast charger or computer port) and a different USB-C cable you know works. Plug it in and watch for the tiny red charging light on the side. If it lights up, leave it for at least 30 minutes before trying the power button. If it still won't turn on, try a hard reset: hold the power button down for a full 15 seconds while it's plugged in.
IF THAT DIDN'T WORK The battery might be in a protection lockout. Leave it plugged into the wall charger (with the red light on) for a solid 4-6 hours undisturbed, then try the power button again. Sometimes it needs a long, slow trickle to wake up from a zero charge.
HEADS UP Avoid using those high-wattage laptop or tablet chargers. The D30's tiny battery isn't designed for them, and while it probably has protection, it's safer to stick with a basic 5V/1A or 5V/2A phone charger.