I have had this issue many many times, so I found this post, it has everything to unbrick it:
https://github.com/OnionIoT/Onion-Docs/blob/master/Omega2/Documentation/Doing-Stuff/Advanced/Firmware-Flashing-from-USB-Storage.md
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Best posts made by Faustas Puzeras
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RE: Omega 2+ bricked