How to Open CPT files on a MAC?

I have some old photos in .CPT format. I can't find an app that will convert these files to .jpg or anything that is standard among different database systems.

I thought I'd found it (XnViewMP was supposed to open .cpt files. It no longer does. How can I open and the save in a standard (for today) format?

Scanned the discussions and found nothing posted within the past couple of years.

Help please!

veehbj