Lost Menu on Smartphone

Hi,
some days ago at my iPhone 6+ I see no MENU anymore in Authenticator.
I can not delete old site codes or add new site codes.
I was try to restart the Smartphone and App many times
and also I check for updates, but it′s still the same:
I can see only a blanc grey menu bar on top.

What can I do? What do I wrong?
Or is this a bug?

Thank you!