mint 20 efi boot partition quit booting

[geek at uniserve.com]

I recently installed Mint 20 on a  Samsung 900 series laptop, 128GB 
SSD and 4GB RAM. I pretty much took defaults. The restore went well 
and I had a working system. I finished up work one evening and clicked 
on "lock screen". In the morning the system had apparently hibernated 
(on grid power) and was slowly blinking a blue LED at me. I was not 
able to get a response to the power button so I unplugged main power 
and waited a day and a half until the battery quit. After restoring 
a/c power the unit still would not boot. I booted off the install 
medium (a stick) and ran gparted which showed 2 partitions, one of 
which is the boot and is a 512 meg EFI fat32. The other shows as EXT4 
and works fine I can see data good and so on.

 I used fsck on the boot partition and was told the dirty bit was set, 
no surprise, so I cleared it. This did not help  with booting without 
the stick, the unit just sits there, the hard drive lamp blinks quite 
a lot and as far as I can see nothing happens.

Is there a boot log I can read? a diagnostic or a fix?

TIA

Dave