1.

I put batteries in the unit and it will not power on/I replaced the batteries and it not turn on.

The batteries should be placed in the unit with a positive end, and a negative end facing into a spring. Although the springs are on the same side, the batteries still need to face opposite polarities.

2.

Batteries were replaced, internal light flashes but nothing happens on the screen.

Make sure the batteries are placed in the unit according to the + and – indicated within the battery compartment.

3.

My display says probe off. How do I turn the probe on?

If your oximeter is displaying probe off, it means that it may not be recognizing a finger in the unit, since it is expecting a probe to be attached. At this point, if probe off does not go away, the unit may be malfunctioning. If under warranty, a replacement can be issued.