I replaced the stock battery in my iP 6 with a 3rd battery. After about a year it was degrading. I wanted a good quality...

mid 2015 macbook pro DG. I replaced the OEM battery with a ZYTH battery. After 15 charge cycles I experienced this problem where on wake-up it showed a depleated battery icon on the screen and required power supply connect to wake. I reset the SMC and now it works. Short (minutes), medium (few houes) and long (many hours) sleep not on power and it will wake fine. So sometimes its not a chronic problem. But... maybe it will return. For now, that was my solution. FYI I get 3-7h on the battery - impressive!

We cant just tell you what to do to fix it because we need to know specifically what is wrong. Is is the display, the display cable, is it the circuitry on the display, is the display circuitry on the logic board, etc? You will need to determine what is wrong first. If it were me I'd be looking at the cable from the display to the logic board and ensure its plugged into its respective connectors properly and there is no other damage. Also while in there tighten up the hinges. If that doesn't help then you will likely need to get another display to see if it works. if it works then the display installed died. etc. Perhaps reach out to the people that did the repair...

Without getting into board level troubleshooting, it sounds like it could be logic board issue. The deteriorating trackpad issue could have been a slowly dying component that was drawing too much current and overheating. Eventually this could damage whatever is driving that current from the logic board side. Replacing the trackpad with no effect is further possible evidence. Is the macbook working normally otherwise? One typical issue is it will go into "limp" mode - the trackpad has sensors on it that the SMC uses. If the trackpad sensors are not working the SMC will force the CPU into a mode where it runs at a flat 0.8GHz and the fans run full speed. The idea is that SMC can effectively manage the mac so it forces into a mode that is ultra safe. If the macbook is working fine otherwise (not in limp mode) then it may be that the section on the logic board that interfaces with the trackpad resposible for the pointer function is not working (and that sensor connection and function is intact). You could try...