SDR# never worked for me. Seems others have the same issue.
When you extracted the SDR# archive (since it's distributed in a Zip file) did you make sure to run the
install-rtlsdr.bat file to have it download the necessary dll files? They can't be distributed directly with SDR# itself so they have to be installed/obtained
after you extract that SDR# Zip file.
So many people forget this step and they just figure there's something wrong with SDR# because it won't work without doing that step and running that batch file. This has nothing to do with the Zadig drivers for the RTL-based stick; that's another step that should be done first actually.
So it's technically a 3 step process for SDR# functionality and operation:
- install the Zadig drivers (you'll know if it's done correctly because the installer will tell you, and yes you have to install the driver twice because RTL-based sticks have two components that require the drivers: the first is the tuner itself and the second is the IR port whether you happen to use that or not
- get the SDR# Zip distribution and extract the contents
- run the install-rtlsdr.bat file and let it grab the necessary dll files (it will also grab the latest Zadig driver installer if you haven't acquired it by that point)
Once those three steps are done, I can't think of any reason that SDR# would not work with an RTL-based device of any kind made by anyone. Whole process takes less than a minute typically and you're up and running.