Indexing can fail in several ways. Here are some typical problems:
If indexing ends up in blank screen, there can be several explanations. The most innocent is simple time out. If the database is too large to index on one go, the indexing will fail. The solution is simple: click “Continue indexing” until the indexing finishes. Keep your eye on the number of indexed documents: that should increase after every click.
If the number of indexed documents isn’t going up, there’s a problem. Typical cause is a plugin conflict. Some plugins don’t work with Relevanssi, for some reason. Usually it’s caused by short codes. You can try that by disabling shortcodes in Relevanssi or deactivating a plugin that uses shortcodes. If you do that and try to index, indexing should work. If you deactivated the plugin, you can now activate it again and everything should work (except searching for the shortcode content, which is not in the index, of course).
Successful index, no documents in the database
Sometimes the indexing goes through without problems, but nothing goes in the index (the number of documents in the index is blank or zero). This is likely caused by a database problem, for some reason Relevanssi can’t insert data in the database. Check the database tables: they may be missing or corrupt. Try deactivating and activating Relevanssi again.
For more instructions, see Debugging indexing problems.