I’ve been having the same issue with the current versions of Relevanssi and Role Scoper.
I took a peek and I saw the following:
relevanssi_default_post_ok() has two arguments, the second of which is the post ID, which gets added to the relevanssi_post_ok filter.
Role Scoper has a file called “relevanssi-helper-front_rs.php” that REMOVES relevanssi_default_post_ok from the filter replaces it with it’s own relevanssi_post_ok() function, which only takes one argument – the post ID.
That is, Role Scoper replaces a function that takes 2 arguments with a function that takes only 1.
In my case at least, it looks like relevanssi_post_ok() is always returning false because every time it’s called it’s trying to use $post_ok (which evaluates to 1 each time) as the post ID. Maybe the search works on your fresh installation because, unlike in my case, you have a visible post whose ID is 1.
That’s all I had time for today, but I hope that helps.