Pending edge certificate validation for 3 days

Same issue as over here:

My personal advice in this case, would be to enable DNSSEC signing within Cloudflare.

Next, you need to re-configure your domain’s DNSSEC on OVH, to make sure that it matches the DNSSEC data from within your Cloudflare Dashboard.

In Cloudflare, you can find that information through this magic link: https://dash.cloudflare.com/?to=/:account/:zone/dns/settings

About maintaining / changing DNSSEC at OVH, you may be able to use these pointers:

Securing your domain name with DNSSEC - OVHcloud

ClouDNS: Activating DNSSEC with OVH