Did the panel suddenly shut off, or was it manually restarted at some point?
Have you checked the battery cable to make sure it’s properly plugged in?
Does the panel’s battery appear swollen?
Has the panel been unplugged for a long period of time? If so, the battery can become deeply discharged, which may take up to thirty minutes before the battery has enough power to boot.
If it’s been a while since this panel was used, some things to check can be found in the guide below.