Unknown filesystem type 'exfat' on Ubuntu 22.04

I am trying to mount an external disk on Ubuntu 22.04, and get the following error:

mount: /media/destdrive: unknown filesystem type 'exfat'.

This was working yesterday, but has stopped working since a reboot (!)

It's Ubuntu 22.04 (so exfat should be installed - no need to install eg exfat-fuse), running in a Hyper-V VM on Windows 11.

The kernel is 5.15.0-1014-azure

cat /proc/filesystems doesn't include exfat

Here is the output of find /lib/modules/ -iname '*exfat*':

/lib/modules/5.15.0-41-generic/kernel/fs/exfat/lib/modules/5.15.0-41-generic/kernel/fs/exfat/exfat.ko/lib/modules/5.15.0-27-generic/kernel/fs/exfat/lib/modules/5.15.0-27-generic/kernel/fs/exfat/exfat.ko

Also, I have tried on Ubuntu 22.04 running directly on WSL2 and am getting the same error.

Maybe I have accidentally installed something or done something to stop it working?

Any help in troubleshooting or fixing this would be much appreciated - thank you!