Odd problem getting RasPlex 1.6.0 or 1.6.2 to even boot.

I am at a loss with this issue. I have two raspberry pies (both version B+) and I had RasPlex 1.6.0 running on one of them, but for reasons that I cannot remember I needed the microsd card or the pi, I can’t remember. Fast forward a few months and now the wife wants the television in the bedroom to have plex again. However I cannot get RasPlex to even boot. I always get stuck at the rainbow screen and the pi never boots. I can image the microsd card with Jessie, noobs, openelec and anything else I can find and it will boot, but I cannot get RasPlex to boot. I have used teh graphical installer and I have used my normal way of imaging cards

sudo dd if=<image.img> of=/dev/sdb bs=4M sudo sync

I have tried 1M for the block size, I have tried not specifying the block size, I have redownloaded the image and verified with md5 that the image is good. I know that the microsd card is good as I can image the microsd card with any raspberry pi image and it will boot. I am at a total loss here. I MUST be doing a dumb, but I am at a loss to figure out what I am screwing up.

I’ve only ever seen that when the power supply was under powered or the wrong PI image was selected.

You are using the wrong image, there are two, one for the RPi Model B/B+ and one for the RPi2/3.