No boot / blue light

I recently got a Rock 4 C+ but cannot get it to boot.
I’m trying to load Debian and wine for a windows only system.

HDMI cable, monitor, mouse and keyboard, connect power and green light is constant.
I’ve seen other threads say about a switch by the USBs, I don’t this is present on this model.
There is a button next to the SD card slot, holding for 8 seconds appears to shut off the pi.
I’ve tried shorting across 23 and 25 with no change.

I’ve flashed several software types and versions with no success.
I’ve tried 2 alternative SD cards with no change. Fresh 64GB and a 16GB in use.
I’ve tried 2 alternative USB C cables, with various plugs from 1A to 3A. No changes.

I hope i’ve just missed something obvious and easy to fix