When you publish an Adobe Captivate project as an executable, what is happening under the hood is that Captivate is publishing your project as an SWF format version with the Flash Player built-in. Since the discontinuation of all Flash-based technology, this feature no longer works. Instead, what you should do is publish to HTML5 and upload it for persons to view on the web.
Punlidhing to exe is no longer possible, because it relies on SWF technology. You may be aware of the fact that the Flash Player needed to play SWFs has been depleted everywhere although FLA files still can be created.
Presently there is no alternative for the so useful EXE publishing which could be used to provide projects for reviewing etc. You need to publish to HTML5, upload to a webserver or a LMS (if you want Reporting) and provide the URL to people to view the course.
Totally agree that both error messages are - to remain polite - rather confusing.