It would depend on the age of your Mac and what OS you are using. In 2017 (for 2016 tax prep), the supported Mac operating systems were 10.10 Yosemite, 10.11 El Capitan and 10.12 Sierra. The current supported versions are 10.17 Catalina, 11 Big Sur and 12 Monterey.
The problem is that several of the steps in between dropped support for older applications, especially 10.15 Catalina. If your Mac is running Catalina or higher, it probably can't open a program designed to run on Yosemite.
There is a chance that the program is actually compatible but it is being blocked from running because Apple's built-in security doesn't recognize the software publisher as being authorized (because the 6 year old security certificate is expired). Locate the program icon in the applications folder and right-click or control-click on the icon and select Open from the menu options. You may be warned the program is potentially unsafe with the option to open the program anyway.
