I tested the thermistor following the instructions listed under the F23 error and it tested ok but was still getting the F23 error so I just installed a new one anyhow and I am still getting the error, what do I check now?

You need to ohm the wiring from the thermistor to the control board if both wires have continuity all the way to the board and the thermistor is closed (has continuity) the control is bad.