I am not sure of which user but if the user is a “Cluster Owner” it should be able. May be something was broken when they switch to unified login.
One thing, I note is that your projectID is probably not projectID. Mine looks like 5a6cb…03b161. Also in place of cluster0-1c9u4, you need the real host name, which will look like cluster0-shard-00-01-1c9u4.mongodb.net.
As I wrote the first paragraph above which I stiked out I am reading:
As previously mentioned, the Atlas API uses HTTP Digest Authentication. The details of digest authentication are beyond the scope of this document, but it essentially requires a username and a password which are hashed using a unique server-generated value called a nonce . The username is the API public key and the password is the corresponding private key.
Each Atlas user or application needing to connect to Atlas must generate an API key before accessing the Atlas API.
Please note that this also new to me. I used the logs from my local servers before but I never had to get the logs from an Atlas cluster.