Editing vocals on an old track

I have an old audio track that I converted from M4A to a WAV file. I was trying to lower the vocals so they are faint or possibly remove them. I tried using the Vocal Remover effect (which inverts and converts the track to mono), but it did not remove the vocals. I am not sure if the track vocals are center-panned, so maybe that is why it didn’t work?

Does anyone know how to remove vocals another way? I would prefer to be able to lower the volume of the vocals within the track if possible.

Thank you!

Vocal Removal Plugins - Audacity Wiki.