Branch Subdomain Certificate Issue

Our site, app-sidekickgpt.netlify.app, uses a custom domain: app.sidekickgpt.io

The domain is managed by Netlify.

I configured a branch deploy and it worked, but when I check the URL (using the custom domain) I see a certificate issue.

staging.app.sidekickgpt.io

I tried to renew the certificate, but it didn’t work.

How can I fix this?