I really wanted to troubleshoot this but I read on another thread (lost link) that re-installing pihole after manually updating dnsmasq helped in some cases.
So I uninstalled and reinstalled pihole and FTL starts automatically on reboot. I added a comment on the update dnsmasq post in case it helps others:
to uninstall
pihole uninstall
to install
curl -sSL https://install.pi-hole.net | bash
Thanks @deHakkelaar and @Mcat12