That is because the regular engine searches the posts database, which only contains the shortcode to the tables, but not the tables content. Only the index table is capable of getting the shortcodes contents, because WordPress does not store that. The reason you didn’t get results with it, was probably a misconfiguration.
Please consider my suggestions, they might help you resolving the problem.
Also, feel free to add FTP and log-in details, and I will take a look at the issue.
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