Battery Won't Charge after Screen Replacement

I just replaced the screen on an iPhone 5S. After replacement, phone booted fine and worked great for about 1 day. I'm not positive, but I think it even charged at some point because it lasted for about 24 hours after the repair. However, now it won't charge. When pushing the power button, I get the low battery icon with lighting symbol indicating it needs to charge. When plugged in, the lighting symbol goes away but low battery remains. I've had it plugged in for hours. At one point I did get it to boot up. Battery indicator showed 3%, then went to 10%, then down to 1% where it stayed for quite a while (maybe an hour or so) but eventually it shutdown and is now back at the low battery icon. Is this a coincidence or does it have to do with the screen replacement? I did reopen the case and recheck the battery connector. It appears ok. Should I invest more money for a new battery that may or may not work? Any advice is appreciated!

Thanks!

Mark