On some of the newer Versions of Mac OSx, Song Surgoen5 may be blocked by your File Vault setting.  The link below shows you how to turn off File Vault on your Mac:  https://support.apple.com/guide/mac-help/turn-off-filevault-on-mac-mchlp2560/15.0/mac/15.0

If you continue to have problems installing Song Surgeon, and haven't already done so, please complete a support ticket.