Hi @Anonymous User
According to NowTV over on Twitter, they seem to be having some sort of technical issues on their website when dealing with certain customers accounts which appears to be going on for at least a week (don't know if updating bank card details on their system is one of their problems).
They reckon they are working on it based on their tweets.
The only things i would try if you haven't already done them, is use a different internet browser (Microsoft Edge always seems to work for me).
Or if you have a smartphone with mobile internet data on it, use the mobile data with the Fire Fox internet browser on your phone when going to the NowTV website in an attempt to update your details.
Sorry i can't offer any further help and i don't know if the above suggestions will work or not.
