Due to thunder store mod manager not properly installing the songs you must manually install the songs; download this mod manually, extract the zip and paste in the BepInEx folder. Now you will see a new folder in that BepInEx folder named "Custom Songs" copy that folder and paste it in this location remember the user & thunderstore mod manager profile folder is different for you then the one mentioned in this listing:

C:\Users\username\AppData\Roaming\Thunderstore Mod Manager\DataFolder\LethalCompany\profiles\yourprofilename\BepInEx

Then launch the game using thunderstore mod manager!