start4.elf not compatible on Raspberry Pi 4 rev 1.5 board (fix)
found fix for it https://github.com/raspberrypi/firmware/tree/master/boot I copied just these 16 files (fixup*.dat and start*.elf) over from latest raspbian to firmware & it booted fine fixup.dat fixup4.dat fixup4cd.dat fixup4db.dat fixup4x.dat fixup_cd.dat fixup_db.dat fixup_x.dat start.elf start4.elf start4cd.elf start4db.elf start4x.elf start_cd.elf start_db.elf start_x.elf