When installing the clang-format visual studio plugin sometimes it won't be loaded correctly (some users seem to have the same issue) and we must do
devenv.exe /updateconfiguration
in order to fix the installation (normally visual studio should automatically execute this command whenever you install a plugin).
This issue seems to come from the fact that the plugin manifest does not list a VsPackage as an asset.
After adding it to assets list (code change in this review) installation of the plugin was working and when uninstalling the plugin visual correctly ask to restart it (that was not the case before).