DIAGNOSIS Battery protection mode is active. The internal lithium battery voltage dropped too low, likely from being stored discharged.
FIX Trickle-charge it with the included AC adapter. Plug it in. Let it sit for at least 2-3 hours with no load. The screen should eventually wake up and show normal charging progress. This can take several hours.
IF THAT DIDN'T WORK The AC wall outlet or adapter could be faulty. Try a different outlet. Confirm the adapter's LED is on. If the unit still shows no signs of life after 6 hours, the BMS may have a hard lock.
HEADS UP Never store this unit at 0% charge. For long-term storage, keep it at 60-80% charge. A completely drained lithium battery can be permanently damaged.