How To Connect OnPremise NAV to PowerApps/PowerBI Content Packs

Having problems creating a connection to NAV on-premise in PowerApps and connecting to any of the NAV PowerBI content packs. Am getting authorization errors.

Does anyone know if the NAV instance/service have to be configured with the NavUserPassword authentication in order for this to work? Does the data gateway have to be installed (it is not but SSL is all set up, I think correctly). I have been trying this for days and ours is set to WIndows authentication. Outside the firewall, I can use the Get Data command to connect PowerBI to the NAV data, can also use the NAV Webclient and the Windows 10 client app and successfully connect to NAV data. However, if I try to create a Connection in PowerApps or use 1 of the NAV content packs in PowerBI, I get authentication issues.

Just read the post:

In it the author mentions that "The DynamicsNAV90_NUP service has been configured with the NavUserPassword authentication."

Could that be due to the NavUserPassword vs Windows authentication?