Hi,
First I would make sure that the index table is correctly configured, and it is indeed enabled. A usual issue is, that users forget to enable the index table engine, and while it’s generated, it is not in use.
If this is correct, then try searching a few words from a post/page where a tablepress table is available. The plugin should return the posts/pages where the table is located.
If nothing works, then please add temporary back-end and FTP details, and I will debug the issue locally.