Papermark signup fails on Vercel with Upstash rate limit error + custom domain not working #1956
Description
We are facing issues while hosting Papermark on Vercel. The application deploys successfully, but the signup process fails.
Issue 1: Signup / Authentication Failure
During user signup, we encounter the following error in the Vercel logs:
Rate limiting error: TypeError: (intermediate value) is not iterable
at checkDenyList (/var/task/node_modules/@upstash/ratelimit/dist/index.js:635:44)
at async Promise.all (index 1)
at async RegionRatelimit.getRatelimitResponse (/var/task/node_modules/@upstash/ratelimit/dist/index.js:838:116)
at async RegionRatelimit.limit (/var/task/node_modules/@upstash/ratelimit/dist/index.js:753:29)
at async c (/var/task/.next/server/chunks/1224.js:1:7448)
at async Object.signIn (/var/task/.next/server/chunks/1224.js:3:4238)
at async Object.signin (/var/task/node_modules/next-auth/core/routes/signin.js:93:38)
at async AuthHandler (/var/task/node_modules/next-auth/core/index.js:230:26)
at async NextAuthApiHandler (/var/task/node_modules/next-auth/next/index.js:18:19)
This appears to be related to Upstash rate limiting during the signIn flow.
We have already:
Deployed successfully on Vercel
Added the Resend API key in Vercel environment variables
However, the issue still persists and signup does not complete.
Issue 2: Custom Domain Not Accessible
Additionally, we are unable to use a custom domain. The application is only accessible via the default Vercel domain, and requests to the custom domain do not work as expected.
Help Needed
Could you please help clarify:
✅ Required environment variables or configuration for Upstash rate limiting
✅ Whether this error is expected when certain env vars are missing
✅ Any additional setup required for signup/authentication on Vercel
✅ Proper steps to enable and configure a custom domain with Papermark