Issues after battery replacement

Hi,

Help please.

I changed the battery on my phone (D802), and when I rebooted all worked fine except for the loud speaker.

I opened the phone up again assuming I must have reseated something incorrectly. Put it all back together again and now I cannot get the thing to respond at all.

If I plug in USB power the LED flashes on an 8 red flash cycle. But other than that no sign of life. I have pulled apart reseated all connectors I've touched.

There's no obvious sign of damage anywhere, but it would appear my clumsy fingers have broken something.

Any advice on what my problem might likely be, or how to proceed would be greatly appreciated.

Thanks

Bob