SSL Problems in C#

[TheForestGump]

DeepLHelper.cs.txt
frm_DeepL.cs.txt

Hello ... I've been trying for hours to do a test translation via the API with C#. Both with .NET 4.8, as well as with .NET Core 6.0. This via HTTPClient, WebClient, NugetPackage and HTTPWebRequest. I always get the error message that no protected SSL channel has been opened. I have installed all certificate handlers. My code works against other SSL APIs ... only against the DeepL-API I do not get a call ... Can someone please help?