Hi, I've been using the Optus app to check my usage for a while and it works great, however, every time I log in with my email and password it suggests that I set up a 4 digit pin code instead. It lets me choose a pin, then askes me to confirm the pin, but after doing so it just keeps giving me a message that says 'oops something went wrong'. I'd like to use the pin because it would be easier but it never seems to let me set it up! I wish it would at least stop asking me to do it every single time if it's not going to work anyway!!
I would try uninstalling the app and then reinstall it.