May I ask what is your domain name?
Has this been resolved, or you still have some issues?
Furthermore, before moving to Cloudflare, was your Website working over HTTPS connection?
If so, did you had an valid SSL certificate installed at your origin host / server which covers both your naked (root) domain any any other needed sub-domain like www, mail, etc.?
May I ask what SSL option have you got selected under the SSL/TLS tab at Cloudflare dashboard for your domain ( Flexible, Full, Full Strict … )?
Did you contacted Cloudflare Support in the meantime?
Are the DNS records proxied or (DNS-only) for your
www.domain.com at Cloudflare dashboard?
In the meantime, you could try to flush the dns for
yourdomain.com using below tools for the desired (A?) type of the DNS record (selected from the dropdoen menu):