The flashing LED (and possibly also the whistling sound) indicates that there is a problem with the power adapter. See this thread: INFO: What do the different LED colours mean? Are you using the charger and cable that came with the PPM?
I have checked the article and I definitely have the red/blue light flashing.
However the unit is charging, could it only be an issue with the adapter or cable?
I don’t think have a charger in the house that could provide enough power to test it out unfortunately.
I have a MacBook from 2019, 30W charger with the following specs so I don’t think that will do
If the unit works well and you have no other problems with it, it could well be only the charger and/or the cable that is the problem. I don’t think that the Apple charger is powerful enough to use with the PPM, but you could try and see if that helps. Worst case scenario is that nothing happens, which will make us no wiser.