If you are unable to access the login page for mywifiext, then you must bear in mind that the website for mywifiext.local is not like every other website you open on a regular basis. This is a local address that will open up the Netgear extender setup settings. It is therefore very important for you to link your device to the internet with an ethernet cable or to link wirelessly while connected to your new extender setup in order to access the web address.