I am replacing the lightning port flex cable and screen on my sisters iPad mini 5. the port was ruined after what looked like the iPad was pulled by her baby, while pulling the charging cable in the opposite direction.

I took the iPad apart and was able to use low melt solder, the NF.Mini Pen and some hot air to remove the broken flex cable. I was then able to resolder the flex cable to the motherboard and reassemble to test. the iPad was dead and when turned on, showed the charging cable and battery icon. it wasn't taking a charge, so I used the NF. Mini Pen to reheat/reflow the flex cable and reassembled. when I plugged the cable in, the battery icon appeared in the middle of the screen, meaning it was charging (or at least the port recognized the cable plugged in) so it appeared it was working now. I let it sit for about an hour and came back to it and this time the screen won't turn on, no battery icon. I checked the screen flex cables, nothing unseated. I found this funny since it was registering a charge before and appeared to be working but now seems totally flat and not working.

I took it apart again to check my flex cable pads and gave them a once over with a fresh coat of solder to ensure they were all seated properly, everything seemed fine.

I tried testing with a multimeter to see if the battery flex cable was receiving voltage, but I was unable to accurately, so I ordered an inline voltage/amp meter to plug into the charging cable to see what voltage and amperage the battery is pulling once plugged in (if anything).

any other ideas what would cause the screen to no longer be working after it was after the first test? anything else to check for? I followed Alex's guide from one of his videos replacing an iPad mini cable and it pretty much went the same. I even made sure the pads were lined up properly (and it appeared they were from the charging icon working).