# Symptom
On your custom production domain, Clerk components render nothing and the browser console shows failed_to_load_clerk_js.
# Confirm the cause
1. Open the dashboard's Domains page and compare its required DNS records against your DNS zone. For a production custom domain you need the CNAME record for the clerk subdomain exactly as shown.
2. Check propagation: the record must resolve (not NXDOMAIN). DNS can take up to 24 hours, so a record added an hour ago may simply not be visible yet.
3. Confirm the clerk-js script URL on your clerk subdomain returns 200 in the browser.
# Fix
- Add the exact CNAME from the dashboard, wait for propagation, then retest. Do not change code while DNS is still propagating; you will chase a ghost.
- While developing, use the development instance (accounts.dev URLs), which needs no custom DNS at all.
# Verify
The script URL returns 200, the console error is gone, and the sign-in component renders on the custom domain.