Prod deployment issue. Invalid runtime error

[abcd-ca]

I have my project working locally (running with vercel dev but when I deploy (vercel --prod), the build gets stuck here:

Error: The following Serverless Functions contain an invalid "runtime":
  - api/calendar/event/[id] (provided)
  - api/calendar/event (provided). Learn More: https://vercel.com/guides/serverless-function-contains-invalid-runtime-error

Any insight would be appreciated.