MogngoDB 7 with TTL index is not removing expired documents

I have a collection with documents that contain two fields:

{
    "needsProcessing" : true,
    "lastUpdated" : ISODate("2024-08-17T19:09:46.099+0000")
}

I have a Partial, TTL index as follows:

{
    "v" : 2.0,
    "key" : {
        "lastUpdated" : 1.0
    },
    "name" : "lastUpdated_1",
    "background" : true,
    "partialFilterExpression" : {
        "needsProcessing" : false
    },
    "expireAfterSeconds" : 432000.0
}

Yet the TTL thread never seems to run

{
    "collSubpassesIncreasedPriority" : NumberLong(0),
    "deletedDocuments" : NumberLong(0),
    "passes" : NumberLong(0),
    "subPasses" : NumberLong(0)
}

Things that have not worked so far.

• I have tried creating a simple TTL index without the partial filter.
• I have tried restarting the Mongod service.
• I have deleted and recreated the indexes multiple times.
• I have stopped all writes and reads to the DB thinking maybe it was overloaded.
• I have checked the mongod.log, and there are no TTLMonitor entries.
• I am running manual deletes using the index now just to make sure the index itself is correct and to keep the data cleaned up.
• I have looked at various posts here regarding TTL indexes, but none seem to apply so far.

Full disclosure, this server started as part of a replica set, but we removed the replica set and when I run rs.status() I get :
MongoServerError[NoReplicationEnabled]: not running with --replSet
Is there anything I can do in MongoDB 7.0.12 to kick off the TTL thread manually? What am I missing?