I got an error when loading db.json
I met the same problem, but fixed by uninstalling json-server module installed with --save-dev. Try making read the module as a global one.
I met the same problem too, and I already installed json-server with -g.
I'm not sure if this is the same issue as this, but I fixed this problem by upgrading node version and re-installing json-server.
Hope those information will also help you.