Hello,

I am attempting to implement JWT Grant authentication for my DocuSign integration in a developer account (demo.docusign.net). I consistently receive the following error when making API calls (e.g., oauth/token endpoint):

"Authenticatie mislukt (400): no_valid_keys_or_signatures"

This translates to no_valid_keys_or_signatures.

Here's what I've done so far:

1. I have created an RSA Keypair within my DocuSign developer account for my Integration Key.
2. I am using the Private Key from this newly generated keypair. I have confirmed that it's copied completely, including the -----BEGIN RSA PRIVATE KEY----- and -----END RSA PRIVATE KEY----- headers/footers, and that there are no extra spaces or missing line breaks.
3. I have correctly set my CLIENT_ID (Integration Key), USER_ID (API Username), ACCOUNT_ID, and DOCUSIGN_BASE_PATH (https://demo.docusign.net) in my application's environment variables.
4. I have performed the required user consent grant by navigating to the consent URL (https://account-d.docusign.com/oauth/auth?...) and accepting.

Despite these steps, I continue to get the no_valid_keys_or_signatures error.

My question is: What are the less common or more subtle reasons that could cause the no_valid_keys_or_signatures error even after generating a new RSA keypair and ensuring proper copying of the private key and correct configuration of all IDs? Is there any specific troubleshooting step I might be missing on the DocuSign side to ensure the Public Key is correctly associated and valid for my Integration Key/User ID combination?