I have a Panasonic TH-37PD25. I have power to the TV but no picture?

Please help.

http://service.us.panasonic.com/opermanpdf/TH37PD25.pdf In case you need.
How do you know you have power? an LED on TV lights? a meter?
Do you have any sound?
I looked at the Manual and didn't see another Power switch on the back?
Is this a new installation, or it just happened?

The TV will come on (led's) and power light on TV. Screen will turn grey. No sound. This is the first time this has happened.

Thank you.