Phone not autofilling password/passkey for only one app (opens in new tab)

Hi, I really need some help\. I have a Blu G91S Android phone that is suddenly refusing to autofill my password - and passkey that I set up - for only one app, my mobile banking app\. There had been no problem for two years, now suddenly it won't autofill\. It is ONLY this one app - every other app gets autofilled, and the ironic thing is my backup phone - a Blu 64 - is autofilling this password and passkey with no problem, so it's not an issue with the bank, and I have talked to their tech\....