Serviceaccount to deploy autorisation between PowerAutomate and Jira

Hello,

I am a Jira administrator. We are trying to set up an automated process using the Jira REST API with a dedicated service account, but we are unable to authenticate successfully.

Issue Details:

When attempting to verify the service account's credentials by making a request to the /rest/api/3/myself endpoint, the API consistently returns a 401 Unauthorized error with the message: Client must be authenticated to access this resource.

This occurs even when using a newly generated API token and the standard Basic Authentication method.

Steps to Reproduce:

1. A new API token was generated for the service account.

2. The string email:api_token was Base64 encoded.

3. A curl request was made as follows:

1 curl -v -H "Authorization: Basic <base64_encoded_string>" https://<domain>.atlassian.net/rest/api/3/myself

1. The response is a 401 Unauthorized with the body: Client must be authenticated to access this resource.

Additional Context:

Our ultimate goal is to access the /rest/api/3/issue/createmeta endpoint. When we try to access it, we receive a different error: {"errorMessages":["You cannot create issues in this project.","You are not authorized to perform this operation. Please
log in."],"errors":{}}. We believe this second error is due to project permissions, but we are currently blocked from troubleshooting it because of the fundamental authentication failure.

Troubleshooting Steps Already Taken:

• Verified the service account exists and is active in our Atlassian organization.

• Generated a new API token and ensured it was copied correctly.

• Confirmed the correct Base64 encoding of the email:api_token string.

• As the Jira administrator, I have reviewed the project permissions for the project and am aware of the need to grant "Browse Projects" and "Create Issues" permissions to the service account's role.

Our Request:

Could you please investigate from your side why REST API authentication is failing for this service account? We need to understand if there is an account-level restriction, a configuration issue on our instance, or another reason that would prevent a
valid API token from being accepted for this specific user.