I did find the same problem/topic asked in the past (May '21), but mine still isn’t working. I’ve followed the Cloudflare instructions on the Obsidian site to a T and that forum topic – so I must just stupidly not know what I’ve missed.
I have 2 CNAME’s set up, one for my site.com (with no “www”) and another one for “www” – both pointing to publish-main.obsidian.md. Proxy status on, TTL on auto for both.
Ok – I found another forum topic w/the same problem and they toggled the encryption from Full to Off, then to Flexible then back to Full. I did that, AND I removed the www from my URL in Obsidian and it’s working now. The field actually gives you the “www” as an example when you enter the URL in Obsidian so that’s what I did. Of course, once I post a help topic I would fix it right afterwards. Anyway, here it is for posterity.