Because of Saurik stop support purchase in cydia.(so don't ask me why you can't purchase in cydia)
Saurik's license system is only support Firmware <= 10.3.x
If you purchased LocationFaker、RouteFaker、FakeStep, you can use it under iOS11 with cydia account linked.
Beacuse of *X is rewrite, and compitable with iOS11, iOS12, iOS13.
So if you want use LocationFakerX、RouteFakerX、FakeStepX upon iOS11, you must purchase it. Like other tweaks (like:Callbar&CallbarX...)