Cannot restart from hard drive after using TechTool Pro on eDrive.

I restarted my computer on the eDrive to run TechTool Pro. Now, I cannot restart from my hard drive. The eDrive is on system version 10.11.6 and my hard drive is on system version 10.13.*. The startup disk panel doesn't show the HD. Restarting while holding C does nothing. I've tried the Terminal command: sudo bless -mount /Volumes/Macintosh HD -setBoot
But, that does nothing. How can I restart from my hard drive?