KV Storage: Having authentication issues even though my API Token has the appropriate permissions

As the title says, we are seeing “Authentication error” with code 10000 whenever we attempt the following request:

curl --location --request PUT 'https://api.cloudflare.com/client/v4/accounts/MY_ACCOUNT_HERE/storage/kv/namespaces/MY_NAMESPACE_HERE/bulk' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer MY_TOKEN_HERE' \
--data '[
    {
    "base64": false,
    "expiration_ttl": 300,
    "key": "My-Key",
    "value": "Some string"
  }
]'

This example is based on the docs (https://developers.cloudflare.com/api/operations/workers-kv-namespace-write-multiple-key-value-pairs).

We’ve also tried the following, with no avail

curl --location --request PUT 'https://api.cloudflare.com/client/v4/accounts/MY_ACCOUNT_HERE/storage/kv/namespaces/MY_NAMESPACE_HERE/values/my_key' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer MY_TOKEN_HERE' \
--data '{"data":"whatever"}'

However, we can successfully read existing keys and validate the same token as correct using the API.

These are the permissions assigned to the token:

Anything we are missing here? Thanks!

Does the user who created the API token have write permissions on the account? Are you able to write individual keypairs using the dashboard from that user?