File '/boot/vmlinuz-5.4-x86_64' not found

I’m a newbie, found nothing when searching topics, sorry.
Upon last update of various software my laptop can’t boot. Black screen, with 2 messages:
error: file ‘/boot/vmlinuz-5.4-x86_64’ not found,
error: you need to load the kernel first.

After those 2 initial error messages I also get a third one:
error: Failed to boot both default and fallback entries.

I’ve noticed that date and time settings were off by several hours, and I have adjusted them now.

So I’m doing the diagnostic tests. From what I can see my Dell Wireless is not working. And there are some issues with Memory test: it aborts. The rest seems good.

Guys, I have no idea. I’m trying to use the external harddisk to try and boot, but to no avail.

Boot: UEFI: SAMSUNG SSD PM851 2.5 7mm 256GB. Legacy option ROMs is disabled. Secure Boot is disabled. I’ve tried to add boot option with USB but have no idea how to do it.

Please bear with me, if you need more info, let me know and I will provide it.

Is there anything I can do via Grub?

boot on your USB iso manjaro
open a terminal and a browser on this topic

return all line errors , and exit to quit chroot

sudo manjaro-chroot -a ( type 1 if only one line 0 appears )
mkinitcpio -P
pacman -Syy
mhwd-kernel -i linux57
mhwd-kernel -i linux58
exit ( quit chroot )

Many thanks, Stephane. I’ll do that, from my old Mac. Question: I’m not losing any of my data, am I? Can I dive right back to where I left yesterday just before the software updating?

no loose data for that