Custom Domain Not Working for Signup/Login with Supabase

Help
1

I have a project connected from Tempo Labs to Vercel using a custom domain https://www.linkcards.ai/

I integrated Supabase as my database.
I’m using Resend.com for SMTP.

Problem
:white_check_mark: Signup/Login works fine on the Vercel preview URL:
:backhand_index_pointing_right: https://tempo-deployment-db8cc8bd-25a6-4817-a872-2cc3e80b07a-tempo-labs.vercel.app/

However, it does NOT work on my actual custom domain :backhand_index_pointing_right: https://www.linkcards.ai and it shows an error when I click on sign up “Login failed: Failed to fetch”

I want signup/login functionality to work fully on my custom domain.

Possible Checks Already Done:
:check_mark: Custom domain is connected to Vercel.
:check_mark: Supabase Redirect URLs Configured properly.
:check_mark: SSL Certificate Working fine.
:check_mark: Preview deployment logs No errors.

What could be causing this issue, and how can I resolve it?

2

The domain troubleshooting guide can help with most custom domain configuration issues. You might be able to use that guide to solve it before a human is available to help you. Then you can come back here and share the answer for bonus points.

You can also use v0 to narrow down the possibilities.