No matching index for proposed shard key

I’m having trouble sharding my products collection the sku index i’ve created. Can someone direct me with what i’m doing wrong?
The index i’ve created on the collection is as follows:

mongos> db.products.getIndexes()
[
        {
                "v" : 2,
                "key" : {
                        "_id" : 1
                },
                "name" : "_id_",
                "ns" : "test.products"
        },
        {
                "v" : 2,
                "key" : {
                        "sku" : 1
                },
                "name" : "sku_1",
                "ns" : "test.products"
        }
]

But when I run the command, it fails to find the index I specify:

mongos> sh.shardCollection("m103.products", {"sku": 1})
{
        "ok" : 0,
        "errmsg" : "Please create an index that starts with the proposed shard key before sharding the collection",
        "code" : 72,
        "codeName" : "InvalidOptions",
        "operationTime" : Timestamp(1604023369, 10),
        "$clusterTime" : {
                "clusterTime" : Timestamp(1604023369, 10),
                "signature" : {
                        "hash" : BinData(0,"pq9qaUYwVJ+UxnzzR/8Hblikzzk="),
                        "keyId" : NumberLong("6889217582478393373")
                }
        }
}

Turns out I was using the wrong database.