Getting ERR_CERT_AUTHORITY_INVALID error

Hi, I’m trying to install and connect to my Misskey instance and I’m facing an ERR_CERT_AUTHORITY_INVALID error. I tried following the instructions in this link (https://www.digitalocean.com/community/questions/getting-err_cert_authority_invalid-error) but it didn’t work. I used the certificate and key provided by Cloudflare. The path of certificate is correct, I restarted nginx, but why doesn’t it work? Any answers would be appreciated. I am attaching a picture for your quick understanding.

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name anarkia.dev;

    ssl_session_timeout 1d;
    ssl_session_cache shared:ssl_session_cache:10m;
    ssl_session_tickets off;

    # To use Let's Encrypt certificate
    ssl_certificate     /etc/ssl/certs/cert.pem;
    ssl_certificate_key /etc/ssl/certs/cert.key;

    # To use Debian/Ubuntu's self-signed certificate (For testing or before issuing a certificat>
    #ssl_certificate     /etc/ssl/certs/ssl-cert-snakeoil.pem;
    #ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key;

source: https://misskey-hub.net/en/docs/for-admin/install/resources/nginx/