Hi Alex,
Generally results pages are not prepared to handle results other than custom post types (posts, pages etc..). Ajax Search Pro bypasses this by converting the user results to “fake” posts with a fake ID with the title and the URL set to the original result.
Most of the themes can handle that, but there are cases where it is simply not possible to do without making changes to the core theme files.
If you have FTP access and a child theme active, I can take a look at the theme file structure to see if there is anything I can do about it.