JanusGraph index stuck in "INSTALLED" state after running REGISTER_INDEX command

I'm trying to create a composite index on the title property in JanusGraph using the Gremlin console.

Here's what I've done so far:

1. Created the title property key.
2. Built a unique composite index on this key named byTitleUnique.
3. Waited for the index to show in the INSTALLED state using

mgmt.getGraphIndex('byTitleUnique')

4. Attempted to update the index status to REGISTERED using the following commands:

mgmt = graph.openManagement()
mgmt.updateIndex(mgmt.getGraphIndex('byTitleUnique'), SchemaAction.REGISTER_INDEX).get()
mgmt.commit()

After running the command and waiting a long time (even over an hour), the index status still remains in the INSTALLED state.

As per my understanding, after this step, I should be able to Reindex and then Enable the index. But since the index isn’t moving past the INSTALLED state, I'm stuck.

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Questions:

• Why isn't the index transitioning from INSTALLED to REGISTERED after running the command?

• Is there anything else I need to do to make this transition happen?

• Could this be related to the backend (I'm using Cassandra and Elasticsearch)?

Any help or insights would be appreciated.