Power troubleshooting and test issues

I received this phone and it can not turn on. His owner does not know the main problem. After i tested it i didn't get an answer. Probably i have forget one test step, can anyone help me by telling me the steps should i do to know the source of problem and fix it?

His owner told me that it was screen problem and the screen is like new and when i test it on power supply on 4.5 v the amperage dosen’t change from 0 A. Can it be an ic power problem?