For this error, we have some suggestions for you, please try and check if they help:
 Please confirm that the source files can be played normally in iTunes/Music.
 Should you encounter any of the situations as described below, please try the detailed solutions for a try:
-- Situation 1: The songs play for about 20 seconds in iTunes/Music, then skip to the next song for converting and end up with "conversion failure".
Solution: Please check whether the system is connected to any external audio device. If so, please disconnect it (including the audio devices connected by Bluetooth, like speakers or headphones). Then restart your computer and convert again.
-- Situation 2: Conversion progress for a single song performs normally, but fails when it is almost completed.
Solution: For macOS 10.15 users, please go to System Files -> Security & Privacy to see if Files and Folders has been granted access to the relevant Documents directory. If it’s not found here, please perform the reset operation.
Search "Terminal" in finder and open it up. In the Terminal application, execute the following command to reset the access permissions of Documents.
tccutil reset SystemPolicyDocumentsFolder "com.audifab.drmmusicconverter"
-- For other situations, please delete the driver file under "/Library/Audio/Plug-Ins/HAL/MMAudio Device.driver", open terminal, and enter "sudo killall coreaudiod" command. Now relaunch AudiFab for a try.
Or directly go to "Menu > Help" and select "Uninstall the Recordinig driver", and then reboot your Mac for a try.
Haven't resolved your problem? Feel free to contact us via Email: firstname.lastname@example.org.