Thanks for the reply. I’ve disabled the DNSSEC option at my registrar (OVH).
However, I’ve other 4 domains (with the same registrar) and they don’t suffer from the same issue. It’s strange that only this one does. I’ll wait and see if this fixes the issue.
On top of what @cscharff wrote, you should also fix your server configuration, as you do not have SSL there either yet. Your server needs to be working fine on HTTPS first.
Thanks for the reply @sandro. I already tried to generate SLL cert at the server side (via Lets Encrypt) but it fails due to Cloudflare inability to generate the universal certificate. For some reason Let’s Encrypt cannot validate that the domain is linked to the IP I specified in the A record.
The Cloudflare certificate should actually not matter in this context. If anything, such a configuration could often be an additional obstacle to getting an LE certificate.