If software fixes don't work, the rugged nature of this phone is the cause.
This resets the battery management IC. I’ve seen this work on three different Power Armor 13 units. How to fix ULEFONE Power Armor 13 black screen
Before sending it off, connect it to a PC and press Power + Volume Down. If Windows makes the “USB connected” sound, back up your data using scrcpy (screen copy tool) — you can mirror the black screen to your computer. If software fixes don't work, the rugged nature
If none of those work, proceed to the hard resets. If software fixes don't work