[Avatars] Changed the default avatar image files but the old ones are still displaying

We changed the default avatar image files but the old ones are still displaying, even for brand new members. I notice they are loading from i0.wp.com/mydomain.com/wp-content/plugins/avatars/avatars-files/images/... Is there any way to clear this Gravatar cache? If that is what's going on, I can't find any Avatars settings in the network dashboard.

FYI: We just discovered that Hummingbird's “Gravatar Caching” was on. After clearing the Gravatar Cache, Avatars are still loading from i0.wp…so I deactivated and reactivated Gravatar Caching, the issue still persists.

Also, we do not use jetpack so I have no idea where the i0.wp URL is coming from.