System.Runtime.InteropServices.COMException (0x80040154): Retrieving the COM class factory for remote component with CLSID {..} error: 80040154

I have an ASP.NET Core 3.1 WebApp that controls third party software via DCOM. That worked fine until I updated the third party software to a new version.

Of course, I change the CSID (found in Start - Component Services - Computer - DCOM) from clsid "{2997C622-CCC7-4533-9B0B-06F28D5EEC12} (Older Version ) to clsid "{A9BB03A7-C8C3-492D-A2DF-35307DC438C5} (New Version) After that, I get the Exception: System.Runtime.InteropServices.COMException (0x80040154): Retrieving the COM class factory for remote component with CLSID {A9BB03A7-C8C3-492D-A2DF-35307DC438C5} from machine 127.0.0.1 failed due to the following error: 80040154 127.0.0.1.

If I build the C# WebApp as an x86 Application, I get a different error message “System.BadImageFormatException: Could not load file or assembly” That’s logical, because the Software is a x64 bit Application. (There is no 32 bit). Now I set from “Any CPU” to “x64” to avoid a processor Architecture difference – but the Exception 80040154 remains..

In the Windows Registry is no Entry for the CSID from the new Software Version only for the old one Computer\HKEY_CLASSES_ROOT\CLSID{2997C622-CCC7-4533-9B0B-06F28D5EEC12} I've already tried to create an entry manually. That runs without an exception, but the App hangs up.

Does anyone know a solution to my problem?