RadzenSSRSViewer: Authentication failed because the connection could not be reused

[sarchibald]

As suggested here:

Passing Authentication to SSRS Report Viewer (.Net 5)

Temp solution ... added WinHttpHandler nuget package and then replaced httpclienthandler with winhttphandler. I am now able to view reports in my .net 5 radzen app. https://www.nuget.org/packages/System.Net.Http.WinHttpHandler/

modifying the generated code to use WinHttpHandler rather than HttpClientHandler worked for me.
I also had to turn off using the default credentials, add a new Network Credential to the handler.

            var httpClientHandler = new WinHttpHandler()
			{
                AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
                AutomaticRedirection = true,
                ServerCredentials = new NetworkCredential("myUser", "myPassword, "myDomain")
            };