Only getting charge battery icon, phone won't turn on!

I bought a new battery from iFixit.com back in January and recently the phone will not charge with apple or 3rd party cables only show the black screen with charge battery symbol. It’s been charging from either the wall plug and my computer for two days. This happened once before but after a few days it came back on. Why does this happen? How can I fix it. I am without a phone, again. Lasting 7 months isn’t great for the battery I bought from here!!!! If this is the battery then this place is a rip off.