boot problems: grub has outdated view of partition

[Jim Perreault]

All,

I've a relatively new HP laptop which came preloaded with Windows 10.  I
installed ubuntu in a dual boot configuration, under Legacy mode.  It was
working fine for a couple of months when, after a kernel upgrade, Ubuntu no
longer boots.

After a couple of false starts, I decided to try to boot an older kernel
using the grub command line.   That's when I discovered that grub is seeing
an older version of the partition.   When booting via the install disk, I
see as the list of available kernels:

5.4.0-37, 5.4.0-40, and 5-4.0-42.

Under grub, I see:

5.4.0-26 and 5.4.0-37

Kernel 5.4.0-26 is the Linux kernel on the install disk.  When I try to use
the command line to boot 5.4.0-37 , I get an "invalid extent" error when
setting initrd.   I used the following commands:

set root=(hd0,gpt5)
linux /boot/vmlinux-5.4.0-37-generic root=/dev/nvme0n1p5
initrd /boot/initrd.img-5.4.0-37-generic

And ideas on how to proceed?    Here is some other information:

BIOS Vendor: AMI
BIOS Revision: F.09
Device Firmware: 5CD0120XJF
Xubuntu version: 20.04 LTS amd64

Thanks,

Jim