For the record, I am getting the same issue. My Gravatar works on all other sites I use Gravatar on except XenForo. When I go to change my avatar here on this forum via Username > Avatar, the 'Use Gravatar' option is selected and is displaying my new avatar. However when I click 'Test' and/or 'Okay' to save my settings, the old avatar is still in use.
I hope this helps in finding a fix for this minor issue.
No problem Mike, it's not a major issue of course, but I guess it does run through people's minds whenever they change their Gravatar and it doesn't work on XenForo. I'm glad that you're trying your best to find a solution.
Unfortunately, this definitely appears to be a Gravatar issue. We serve avatars directly from Gravatar, so we're at the mercy of their cache life time. Ok, that should be fine -- it's only 5 minutes. However, they're doing caching beyond that - at the Varnish level most likely, so it's not a client-side issue. If you set additional URL params, you can bust this caching on their end, but only for that URL.
This is something they'd have to resolve. Note that it's not specific to XF URLs. It may be related to the size options they provide and them not expiring the cache correctly. Unfortunately, they don't have any contact form on their site...
Well I've just tried using the links given in various help topics on their Common Questions page but it still doesn't clear the cache or allow for the newly uploaded image to show. I changed my Gravatar a couple of days ago so I guess I can give it a week to see if there is any progress. In regards to not having any sort of contact form or address on their site; they are run by Automattic, so I assume using their contact form would be most beneficial?
How long ago did everyone else update their Gravatars? Just so we can get a specific period of time on how long Gravatars haven't been updated...
If it helps Mike, my new Gravatar is in use on other sites except XenForo... WordPress displays it fine at least.