The library validates certificates against the certifi bundle rather than the Windows certificate store. A certificate signed by an internal company CA, even a Windows certificate, can cause errors. The only exception is if SystemLink explicitly passes the CA certificate path while creating client objects.

To resolve these errors, install nisystemlink-clients 1.6.1 or later. The 1.6.x release line is the last to support Python 3.8. This version of Python bundles with SystemLink Server. Contact your Windows administrator to install the package into the Python environment for the system. For more information, refer to Python Package Installer Behavior for Least-Privilege Mode.