No back light on power up sorta

Bought a used 6s with a cracked screen several years ago. Replaced the screen and powered it up with the screen still separated from the case. Everything seemed to be ok until I closed the case up. The backlight wouldn’t come on after that. I didn’t mess with it for a few months. I took a look at it again, and the battery was discharged. When I plugged in the charge cable the battery indicator came on the display, and would reappear any time I hit the home button. Once it had enough charge in the battery to power up it has the no backlight issue.

How is it showing the battery image but nothing else?

UPDATE

I can do the Home/Power buttons reset. As soon as the Apple logo goes off (using a flashlight to see it), I can hit the power button and the backlight flashes on for a second. I can see the time and date, Iphone is disabled Connect to iTunes.