Hi Yohannes,
I think the issue here should be related with the on premise data gateway connection.
Could you please share more detailsabout the on premise SQL Server connection, are there any errors popped out when add this connection?
In addition, this exception occurred with PowerApp Studio, or PowerApp studio for Web?
Please follow the Troubleshooting part to check the gateway logs first:
Understand op-premises data gateways for Microsoft PowerApps
See if we could get any helpful information from there.
Also if you are using PowerApp studio, then please uninstall it and then reinstall it from Windows Store to check this issue again.
Further, in PowerApp, under Account->Diagnostics->Debug, you could be able to find the App logs, please check to see if any errors logged there.
Besides, Microsoft.IdentityModel.Clients.ActiveDirectory is Active Directory Authentication Library (ADAL), which provides a Portable Class Library with easy to use authentication functionality for your .NET client on various platforms including Windows desktop, Windows Store, Xamarin iOS and Xamarin Android by taking advantage of Windows Server Active Directory and Azure Active Directory. This Library could be installed through the Package Manager Console in Visual Studio, for more information, please see:
Active Directory Authentication Library
Regards