Something isn't right, however the probe will still work even if the Duet is configured for analog mode and the IR sensor is producing a digital output. You won't get the benefit of the probing move slowing down when the probe gets close to trigger height.
Can you confirm that the IR sensor you are using is the differential Mini IR sensor, that I sell through Escher3d.com and is also dole by duet3d.com and their distributors? It should work with black surfaces, unless you have a very old sensor. I have recently tested it with black PrintBite.
Yes I could look at what components are likely to have failed. However, if the green 3.3V LED is not lighting up and/or multiple ICs are getting hot, this typically means that multiple Ics have failed and the board is uneconomic to repair.
See https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe#main for advice on connecting various types of Z probe. If the V_FAN jumper is set to the VIN position then the easiest place to get VIN is from one of the always-on fan connectors.