The most common cause for the menu open and closing quickly, is having manually copied the GSX folders in the Community, so they are not symlinks anymore (as they should be), so the sim is using an outdated version, while our updater is updating its local copy the sim won't use because of the manually created copies. Those can also appear if you restored from a backup, so you might not realize they are not symlinks anymore.
And in any case, when reporting a problem, ALWAYS provide a startup log as well, made according to the Sticky thread on this forum.