The boards are Ultra96v1. They are both able to boot from the standard avnet linux image. That boot take few seconds at most.
When booting from an sd-card with the latest image of PYNQ V2.6 made for the Ultra96v1 the download (done) led stay red and the 4 user leds stay green.
Is there a repo with the v2.5 image for th eUltra96v1 that I can try?
Don’t use Samsung EVO cards or any cards that may be rebranded but actually an EVO, they won’t boot on the U96’s. Use Sandisk if you can, though other makes such as Delkin do work. If that is not your issue, I’m not sure what else to tell you based on the information you’ve given.
Stranger things have happened but v2.6 has been out for a long time now and it was tested on v1 and v2. No one else has reported any issue like this before either.
Even if you loaded a v2 image on a v1 it will at least boot or boot part way, so it’s not that either.