Email address autocomplete stopped working?

I use K-9 Mail on my Android phone (Motorola) and an old RCA Android tablet. Love it.

Except a few weeks ago only on my tablet the email address autocomplete when I was composing emails stopped working. I have to type in the entire email address and then K-9 recognizes it – before I could type in a few characters and would be prompted with a list of matching email addresses to choose from (very handy!).

It still works that way on my Android phone – just not my tablet – and I am pretty sure that K-9 has been updated on both devices.

I did not find a setting to switch that behavior off/on.

Help!

Thanks!