Lockout mode on water heater

I got a call from a client concerning a house that I inspected for him, now has a problem with the water heater being in a lock out mode.
The water heater looked very new with electronic controls & lights on the front down by the burner. Does anyone know what a lock out mode is & how to change it?
It looked like a sealed comb unit with plastic venting.
The seller thinks I did something to it, but actually I did not touch it.

Brand and model number? Tough without a picture or information.

Dirty flame sensor Roy…I’d bet.

Tell him to have it SERVICED…!

Here are a few possibilities.

Rheem
Mod # 42VP40FW
No picture sorry.

Looks like the first thing to try is a basic power reset. Unplug the unit and leave it unplugged for 30 minutes. It gets spendy from there.

If it is electronic controls, is there an LED code showing?

http://rheem.com/product.aspx?id=EC73220D-709B-4723-BD9F-137AF5CE481B

directions and help.

•Control lockout: the user must depress the “up” and “down” temperature buttons for five seconds to unlock the control

Problem with ignition.

Control lockout: the user must depress the “up” and “down” temperature buttons for five seconds to unlock the control