All user profile pictures are failing since I changed the domain name for the site. They also fail to work in "Settings, Discussion, Default Avatar" list. This is the only issues I have found so far...
The WordPress site is physically the same, I just have an old and a new DNS name. If I temporarily change back to using the old domain the avatars work again.
Google Chrome Dev Tools shows "ERR_BLOCKED_BY_CLIENT", I type the URL into chrome, I get the correct gravatar. What is the client, my browser or the WP server? I have disabled AVG on my windows computer without any improvement, and I have disabled all plugins in WP again no improvements.
As far as I can tell there is no server or browser caching issues involved.
Dev Tools shows: Request URL: https://secure.gravatar.com/avatar/caa7f7ac741d667181928dddf7cf2f69?s=32&f=y&r=pg Referrer Policy: strict-origin-when-cross-origin
No Response Headers
If I type "https://secure.gravatar.com/avatar/caa7f7ac741d667181928dddf7cf2f69?s=32&f=y&r=pg" into my browser it correct displays the profile image.
This is the html code for one of those images:
<label> <input type="radio" name="avatar_default" id="avatar_gravatar_default" value="gravatar_default"> <img alt="" src="https://secure.gravatar.com/avatar/caa7f7ac741d667181928dddf7cf2f69?s=32&f=y&r=pg" srcset="https://secure.gravatar.com/avatar/caa7f7ac741d667181928dddf7cf2f69?s=64&f=y&r=pg 2x" class="avatar avatar-32 photo avatar-default" height="32" width="32" loading="lazy" decoding="async"> Gravatar Logo </label>
It was a privacy related Chrome extension (Ghostery):
https://chromewebstore.google.com/detail/ghostery-%E2%80%93-privacy-ad-blo/mlomiejdfkolichcflejclcbmpeaniij
I normally would have picked up the problem but this time didn't, the new domain didn't have any exceptions, Anyway, so the client really was my computer and I hope this helps someone who has the same issue downstream :-)