Re: i have replaced my nokia lumia 820 screen and my phone wont switch on
you just asked 'Why do fools fall in love'
When you say screen, just the glass, or complete LCD assembly?
Your technical level, your ability to perform this has NOT been addressed.
Do you know what you are doing?
Did you follow the video / manual, or wing it?
I'd suggest you search for & download the 'Lumia 820 Service Manual' & give the pictures a glance, the manual a read - you may find your error! ... cause, frankly, we wouldn't know what you did.