"Certificate misses intermediates " when I try to use GitLab Pages integration with Let's Encrypt


I have a Gitlab pages site for a while which I had already set up with certificates from Let’s Encrypt. Recently I noticed there is an integration within Gitlab pages that will automatically renew the certificates.

However when I follow this guide https://gitlab.com/help/user/project/pages/custom_domains_ssl_tls_certification/lets_encrypt_integration.md I keep getting an error saying "Certificate misses intermediates " when I save the settings.

Any help?