Replaced Battery in iPhone 7 Plus, Still Not Working

We had a swollen battery on an iPhone 7 Plus, so i replaced it last night with a 29.00 battery kit from Amazon. It took us no less than 3 hours to do it. I feel like i didn’t re-connect the battery connector correctly. Now the phone will ‘turn on’, but it only blinks the Apple logo. It won’t do anything else, 13 hour later. What can i do or what did i do wrong? At this point, and after the time consuming task of changing it and unscrewing the tiniest screws i have ever seen, i don’t feel like opening it up again. is it save-able or should i just recycle and buy a new one? Also, how do i safely dispose of the old swollen battery and the new one if i don’t use it?

HELP!