Why is the react deployment failing? Using "CI= npm run build" doesn't seem to be working

If the other routes were static files built to
client/build/set-reminder.html or client/build/set-reminder/index.html (for example), they would just work.

If you’re using dynamic routes in your Single Page Application (SPA) then you’ll want to add a _redirects (or netlify.toml) redirect rule that tells all of the paths to load the root file.