Thanks to all who have offered suggestions to help. I swear sometimes I hate how complicated it is to run more than one audio program on a Windows machine.

My solution was simple if mystifying.

I installed ASIO4All which replaced whatever happened to my ASIO driver that ProTools didn't like. As a result of installing a new ASIO driver, I was able to open ProTools without the error windows that previously prevented me from doing so, and in the Playback Engine Menu item, I was now able to switch back to the Yamaha / Steinberg driver that came with my AG06 mixer / audio interface.

Now Band in a Box and Pro Tools work together in harmony and I can back to making music using both programs.

My experience may not help other users, but I appreciate all the suggestions people made and I am ready to explore all the new features of BIAB 2019 and export my files to ProTools to polish them off.

Thanks to all who responded.