Fedora Acer Atom netbook: after software update from version 26 to 27, needed to select new UEFI cert in BIOS

After a software update upgraded an Acer netbook from Fedora 26 to 27, the netbook booted with the error message “no valid boot devices.”

The system was originally installed, then updated, in UEFI Secure Boot mode. Fedora 27 installed a new UEFI certificate in the BIOS, but I had to go into the BIOS to select it as the current default.