HELP! Rpi4 stuck at rainbow stage after firmware update.
As I was having no luck enabling the hardware acceleration functionality in chromium, first tried using sudo rpi-update as suggested here: https://www.raspberrypi.org/forums/view ... 5&start=25 to update the rpi4 firmware. Everything seemed fine during the firmware update and fine after a reboot but chrome://gpu still reported no WebGL harware acceleration. Therefore I thought booting with a brand new raspian-buster image might help. However seems this has essentially bricked my new rpi4. Sequence of events (after firmware update via sudo rpi-update) went as follows:
1. I switched to a new card/buster image; booted without issues first time.
2. Ran the suggested system updates.
3. Rebooted; Now stuck at rainbow stage!
Everything I have tried after this ends up stuck at the rainbow stage , including another brand new card and new raspian-buster image with boot_delay=1 in the config.txt file; also tried booting using NOOBS, same result. Interestingly, same cards boot fine in a rpi 3b+, so definitely NOT an SD card issue. Harware was not touched except to swap out the SD cards and using the same power supply.
I can also confirm that repairing the BOOT EEPROM as described in https://www.raspberrypi.org/forums/view ... i4#p437084 and https://www.raspberrypi.org/documentati ... teeprom.md does not help even though the process seems to be successful (continuous LED flashing after booting from the repair SD). Also 3V3 is fine on the board. Lastly, without a SD card in, the green LED blinks 4 times, suggesting the EEPROM bootloader is fine?
Please help, out of ideas here! Thanks