Before generating the API access credentials, you must verify if the user in question is an environment manager.
To verify, access the logged-in user's data by navigating to the Side Menu>Management>Users, then access the user in question and check if the "Environment Administrator" option is enabled.
If it is, go to Side Menu>Management>Environments.
Click the three dots at the end of the row and access Settings.
Right after, find the Integration API section and generate the credentials.