Neo.ClientErre. Procedure. ProcedureCallFailed: Failed to invoke procedure 'db.index.fulltext.queryRelationships Caused by: java.lang.IllegalStateException: Expected index to come online within a reasonable time.
Where are you running the statement (Neo4j Browser or somewhere else)? Also, what are the parameters you are providing to the db.index.fulltext.queryRelationships() procedure? A bit more information will help me better determine what could be causing the issue!
It sounds like the index could be populating when you try to run the query against it. Could you check by running the SHOW INDEXES query and see if the index shows in the populating status?
Could you wait a few minutes and try running that SHOW INDEXES command again to see if it eventually completes? If not, how long is it sitting in the populating status?