We're aware that some users are having trouble opening CellProfiler on the latest Mac OSX security patch. We're working on resolving this, in the meantime you may want to build from source (see below).
Additionally, some users have reported experiencing issues when opening CellProfiler since updating to macOS 10.15.7. While we are still investigating the problem, we have found a couple of workarounds to successfully open CellProfiler, which you can find here.
Note 1: On Mac, after downloading, put CellProfiler in your Applications folder and ctrl-click (or right-click) and choose Open. Otherwise, you will receive a warning: “CellProfiler can’t be opened because it is from an unidentified developer”.
Note 2: Ignore the warning “Error loading pipeline file” - just click OK.
Note: On Windows, after downloading and launching CellProfiler, if you get the “Windows protected your PC” message, click “More info” to allow you to hit “Run anyway” to install.
Source code available on Github