If you are experiencing Error 1004 problem when converting Spotify music with Sidify Music Converter for Windows, please follow some steps to adjust settings on Spotify preference and see if it fixes your problem.
Please go to Spotify app > Edit > Preferences to open the preference window and follow the instructions below:
If you're using a free account then make sure the high quality streaming is turned off in preferences setting.
Please try to uncheck all the options under Local File column.
Try to clear or delete your local-files cache in Spotify. Just follow the guide below:
In Spotify, scroll all the way to the bottom of setting section and click "Show Advanced settings" button. Then scroll to the bottom of the advanced settings section, and turn off "Enable hardware acceleration". After that, please restart Spotify for a try.
If that doesn't fix the problem, please contact us at: firstname.lastname@example.org. Please also try to provide us with following information for further analysis. We will submit your feedback to our developer and inform you if the solution is available.