A few people have reported on the title, but I don't know the exact cause of the problem. This mod is very simple in structure, just replace the Music file, so the mod itself is is unlikely to have a defect.

Check out the [Steam\steamapps\common\Crypt of the NecroDancer\downloaded_mods]. If there's no [Revibed of the NecroDancer - Suizin.zip] and same name folder, you might not actually have completed the workshop item download, try checking the Steam client's library -> download queue, or reboot steam client / computer and recheck the queue.
If the above file exists but does not appear in the mod selection, trying restart/reinstall the NecroDancer recent version client or checking for integrity. (Check the game property from your library).


If it doesn't work, maybe if you take a little time to wait for Steam to download and process the workshop files and try again, it seems to recognize the mods before you know it.

If you have encountered and solved the problem of the mod not being recognized, please let me know how in this thread.