Bitcoin Core RPC cURL – importdescriptors failing on loaded wallet

I am running the following request to load a wallet.

curl --location 'user:[email protected]:8332/wallet/test_multisig"' \
--header 'Content-Type: text/plain' \
--data '{
    "jsonrpc": "2.0",
    "method":"loadwallet",
    "params": ["test_multisig"],
    "id": "test_multisig_wallet_load"
}'

It returns…

{"result":null,"error":{"code":-35,"message":"Wallet \"test_multisig\" is already loaded."},"id":"test_multisig_wallet_load"}

However I then run this exact request, and receive an error as if the wallet is not loaded.

curl --location 'user:[email protected]:8332/wallet/test_multisig"' \
--header 'Content-Type: text/plain' \
--data '{
    "jsonrpc": "2.0",
    "method":"importdescriptors",
    "params":{
        "requests":[{
        "desc":"pkh(cSQPHDBwXGjVzWRqAHm6zfvQhaTuj1f2bFH58h55ghbjtFwvmeXR)",
        "active": false,
        "range": 20,
        "next_index": 0,
        "timestamp": "now", 
        "internal": false,
        "label": "test_multisig_wallet"
        }]
    }
}'

Error…
{"result":null,"error":{"code":-18,"message":"Requested wallet does not exist or is not loaded"},"id":null}

How can I import descriptors into a wallet so the wallet has a sequence of addresses?