A failed firmware update probably isn't user-fixable.   If it won't turn on at all, it fails the self-test and BID. In that case and you're within first 30 days from Dell's invoice date (not delivery date), the replacement should be new. If it's beyond those first 30 days, it will be refurbished.
I have a brand new Dell UltraSharp 27 USB-C Hub U2722DE. Dell support showed that the U2722DE firmware could be updated (to M3T107). The firmware update failed and I found that the monitor powered off by itself but will not power on. I unplugged everything (video, USB, etc.), changed the power cord, pressed the power button for more than 5 seconds, etc. Let's say I tried everything suggested by the manual but the monitor doesn't turn on anymore, is dead. I know I can replace it under warranty, but I rather fix it than have the hassle of sending it back, waiting for the new one, etc. I have seen the related post by Javier. The solution seems a bit mean (refurbished for a brand new DOA monitor?). Thanks in advance for any suggestions / help, Robert
U2722DE, doesn't power on after (failed) firmware update