Hello it's unlikeley it's the commuincations board but it could be chesck by replacing it (or the cble whatever you think is wrong) if that does'nt fix your problem then could it be (1. It's water dameged or (2. Is there dust inside it?
You did nothing wrong instead you forgot to do something! Just hold down home and power together until you get to apple logo. If you get a white screen just hold down home and power again.