New_kernel_doesn’t_recognize_ufs_gpt_root_file system

Finally got a build world/kernel to complete. Following a
installkernel with a boot -s resulted in the inability
to mount root (/dev/gpt/FBSD15)
It’s a ufs2 filesystem. I booted the 15-CURRENT
usb stick. It recognized it. I performed fsck on
it. No errors.
An attempt to mount it from the new kernel at boot is:
Mounting from ufs:/dev/gpt/FBSD15 failed with error 19.

Can anyone suggest the best way forward please?

Thanks.

—-Chris

-- 
sent from hardware written from and running on FreeBSD