Trying to top up a Spark wireless users account as its run out of data, but having fun doing so...

The laptop brings up a Spark page advising its out of data, and has a Click Here To Topup button... which does nothing. So connected to a hotspot and visit spark.co.nz to try from there, click Sign In, and same issue, just sits there....

How am I meant to topup if I cant log in without being on an active account ? Do they lock down the accounts stuff to Spark IPs only ?