Hi, Bill,
I am not sure what causes your problem, but it does sound like your system cannot identify
the root system so it cannot boot. I happened to have similar problem as you do after dnf
update a few weeks ago, although slightly differently. I did have to fsck my partition
before my system booted successfully. I found one of the posts you may want to check out.
https://unix.stackexchange.com/questions/278385/boot-problem-in-linux
It is when dracut cannot identify root file system. Please let me know if you have this
problem.