https://gplifehacks.com/2018/06/08/dynamics-gp-power-bi-unable-to-connect-to-powerbi-site-contact-your-system-administrator/
Shawn Dorward tackles issues connecting to Power BI from GP.
https://gplifehacks.com/2018/06/08/dynamics-gp-power-bi-unable-to-conn…
Archived post from 2018. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.