Why did my Autopay stop?

Like everyone else who posts here asking why their autopay suddenly stopped, I have been on autopay for years with no issue. My autopay is connected to my checking account, which had other automatic payments taken out before and after when my Comcast autopay should have been taken out. I haven't changed any settings and when I logged in, saw that autopay was still on. The chat line will not put me in touch with a human, just says that my bill is past due (which I paid before starting the chat). I did not receive any communication regarding my bill, so I do not believe there was an error with my payment method, but that Comcast decided to stop my autopay without informing me.