How to classify proposed documents.

I created an index with taxonomies. The taxonomies are query-based with automatic classification. Some documents are not classified automatically.

The detail screen of the document shows by classification: <b>proposed categories</b> taxonomie example thema_1 100%

It’s possible to add the categories manually, but that is not what I want. I tried a re-index and a incremental update, but the documents do not classify. I don't see the documents in the inbox 'Documents to classify' . What is going on? Why doesn’t a re-index or incremental update help? Is there something wrong with the document because other documents are automatically classified?

Can anyone please help me solve this problem?