If the error message "Error: Header overflow" is displayed when calling an API using Postman to obtain an authentication token, it means that the header has exceeded its limit. To resolve this issue, follow these steps:
Modify the environment variables of the operating system. In Windows 10, right click This PC and choose Properties. Click Advanced system settings. On the Advanced tab, click Environment Variables.... In the Environment Variables dialog box, click New... in the System variables area. Configure Variable name and Variable value as follows: