On reboot of my opnsense router it did not tailscale up. I'm not sure if a key expired or what happened. The fix was to first enable ssh, then ssh in and run tailscale up.

enable ssh

In opnsense System > Settings > Administration > Secure Shell > Enable Secure Shell

tailscale up

        
ssh <opnsense ip>
8 # to select shell
tailscale up

Follow the link to log in.

disable ssh

now uncheck secure shell to lock down the opnsense machine.

In opnsense System > Settings > Administration > Secure Shell > Enable Secure Shell