Application login is returning 400s and 500s when deployed on vercel

Problem statement

We have two applications with the same configurations. But in one of them, I got a 500 internal server error.
The site is currently on Vercel. The env variables were set accordingly.


  • .har file will show 400 or 500 based errors
  • there likely won’t be direct calls to Auth0 endpoints. The error is occurring due to an error in how our SDK is instantiating
  • error when reviewing Vercel logs were:
    “issuerBaseURL” must be a valid uri


  • confirming that auth0 endpoints are not being called helped confirm the issue was likely not on our side
  • the app was working locally and only started returning errors when it was deployed to Vercel


  • Vercel read the app’s config variables incorrectly and caused several errors when attempting to use the Auth0 SDK.


  • remove all config variables from Vercel and re-add them