OF OF is demo mode (cooling off)
Check that the child lock is not on by holding ice off for 3-5 sec there should be a little lock symbol
To remove from sales mode press and hold energy saver and freezer temp for 3-5 sec unit you here the "ding dong sound"
If unit is entering sales/demo mode on its own try placing it in child lock mode and see if it enters demo mode by its self if it dose sounds like a main board if it stops only with child lock on its a User interface.
The unit shouldn't be going in to demo by its self
User interface part number da97-11332r
or a bad Main PCB da97-00147b.