# PI4 won't boot

**URL:** <https://forum.core-electronics.com.au/t/pi4-wont-boot/12654>\
**Category:** Uncategorized\
**Created:** [3 January 2022 11:55 UTC](https://forum.core-electronics.com.au/t/pi4-wont-boot/12654 "2022-01-03T11:55:23Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![G177630](https://avatars.discourse-cdn.com/v4/letter/g/f07891/32.png) [@G177630](https://forum.core-electronics.com.au/u/G177630)\
**Post date:** [4 January 2022 11:41 UTC](https://forum.core-electronics.com.au/t/pi4-wont-boot/12654/7 "2022-01-04T11:41:29Z")

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If the green light is ON with the SD card in, then it means the SD card is detected. Check [this thread](https://forum.core-electronics.com.au/t/raspberry-pi-os-bullseye-released/12086/15), Nathan had similar symptoms. The problem was the USB drive.

As Oliver mentioned, all connections, especially HDMI, should be in before powering up the PI. HDMI 0 is the one closest to the power in USB3 connector.

In any case, try using Sandisk or Samsung EVO micro SD cards. I was using a different but UHS 3 class card on my Pi Zero W. It would have issues booting, but the files are readable using an external card reader. Finally switched to a Samsung Evo UHS 1 class. The issue went away.

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