The PSE waveform looks familiar, but the voltage scale of 1kV does not see correct. If this is a true waveform, the timing at the PSE leads me to believe there is a DC disconnect at the PSE.
What is the output of the PD connected to? The PD must draw a DC MPS minimum current to remain on. The LT4293 demo board sets the LED current limiting resistor to draw this minimum load; But the LED load is for demo purposes since the demo board output is open for connection to the application load. The PD schematic show a much larger resistor value who reduces the load current below the DC MPS if JP3 is not connected to anything. The PD must draw more than 10mA to remain on.
，PSE原理图如下图所示
,PD原理图如下图所示
