I have the same issue, I thought it might be as I got a new phone? I had iPhone 7plus, now iPhone XS. Does that make a difference?? I would love to see my bills again?? No idea when they are due or how much without the app!
AGL have no idea, the departments are terrible with communication. I had the same problem it took 10 phone calls to fix. In the end I was told to log in as normal, but then use the Authorisation code not your password. You think it is a simple problem and it is known by a few, they could pass it to the other staff at AGL.
The amount of times my password was reset by AGL to fix this was 5 times. Only 1 person out of the 10 was helpful.
So it worked for 2 weeks, but now I can log in, but can't enter my meter reads, guess another 10 phone calls. Terrible service AGAIN!!!!!
Apologies for the delayed reply!
I'm happy to confirm that this issue was resolved last month. If you're still having issues, please let me know!