Why won't my phone turning on after battery replacement?

I replaced battery in my iPhone 6s plus 3 weeks ago, after battery replacement phone turned on and was working perfectly, on Wednesday set phone down for the evening, did not put on charger. Next day realized it had died over night put on charger all day on Thursday, I left it all day and all night on charger went to use in on Friday to find it would not turn on. I tried holding home and power buttons together at same time and nothing. Then tried to connect to computer. The computer did not recognize the phone. I know the phone was on the most recent software update, and to my knowledge the phone has not been dropped, any other suggestions???