Thread:Project:Support desk/PrefSwitch: Impossible to make running PrefSwitch on brand new mediawiki installation, both local or hosted/reply

Probably help if you told us how you had it configured (like do you have  at the very bottom of your LocalSettings.php - which is needed to enable the link at the top of the page)

Note, that extension was mostly a 1 time thing needed by Wikipedia. I don't think anyone is currently maintaining it, so there could be some bit-rot with the extension itself.