The classic update manager can't be used to update a plugin installed in a global read-only location. It tries to install it to your user plugin location, but when you restart, the global directory overrides the user-specific one. But you can use the update manager to install new plugins.
The classic update manager can't be used to update a plugin installed in a global read-only location. It tries to install it to your user plugin location, but when you restart, the global directory overrides the user-specific one. But you can use the update manager to install new plugins.