[yocto] fstab entry not mounting at boot-up

[Edward Wingate]

My system has a USB-SSD drive and I added this to my fstab:
/dev/sda1  /mnt/drive    auto   defaults,nonempty  0 0

But it doesn't get mounted on start-up.  I can use "mount -a" after
start-up and it mounts successfully.

Everything else in fstab gets mounted on boot.  Does anyone know why
my new entry doesn't?

Thanks for any help.

Ed