I had the same issue not too long ago myself and found the solution in a really obscure place.
When you are managing your hub site, at the very top where your site name is, there is that little down arrow. Click on that and go to content library. Once there, in the upper right hand corner near "New", there are the 3-dots ...
Click on the 3-dots and select "Check for Content Update". It can take a bit to work, but ends up happening is that it updates the cache Esri users to speed up Hub.
Hope that helps.