keyboard was not popping up when I had the BT scanner enabled:
It would work on my Note 3 but not my Pixel 2 XL. To make a veeerrrryyy long story short, on the newer versions of the Android OS there is a keyboard icon in the lower right area of the screen. Tap that icon and a modal will pop up (see my screenshots below). Turn on the Show Virtual keyboard and it should start working with BT turned on.
Not sure which Android version introduced that. My Note 3 is on v5 and my Pixel is on v9.