Have you checked if there are any conflicting plugins hindering the icons work? If not try deactivating any third party plugins,reactivate and check one by one.
Also try clearing the browser cache and reload again.
Let us know if it works.
just noticed all the icons belong to a plugin called ‘ultimate member’. deactivated all other plugins and reinstalled UM, same problem. their tech support says it’s an issue with the theme. UM has over 70,000 installs, might be worth investigating.