I have replaced my iPhone 5s battery and now it won't start. Why?

Had the battery and charge port (bit where the charger plugs into) in my phone replaced today in my iPhone 5s by professionals. Came home to charge up phone, have had the phone plugged into power for 2hours plus and it still hasn't rebooted! The only thing that is appearing on my screen is a battery with a red bar of charge.

How long should it take to charge up a new battery?

I have plugged the phone into the computer and it's not appearing in iTunes, I have tried to hold the home button and the on/off button to reset it and nothing is happening but have had no luck. What else can I do?

Thanks in advance!