Only Silence after removing vocals??

The vocal remover works by subtracting left from right. This removes “centered” vocals which are identical in the left & right channels. It also removes everything else that’s in the center. Inverting & mixing left & right does the same thing.*

If you’re getting silence you have a mono (or “dual mono”) file with identical left & right channels.

…“You can’t un-bake a cake or un-fry an egg and you can’t un-mix audio.” That’s why pros record in multi-track. So they can adjust or edit the different instruments & vocals separately before mixing. And, it’s the same reason you see multiple mics (run into a mixer) in live performances, so that all of the mics can be adjusted separately before mixing.

*Mixing is done by summation so if you flip the polarity of one channel and mix left & right together you are “adding a negative” which is the same as subtracting.

There is some optional frequency-filtering so you can keep the bass (which is almost always centered).

BTW - If you invert one channel and don’t mix, the soundwaves will mix acoustically (in the air). The vocals won’t cancel (for some complicated reasons) but you’ll get some “weird phasing” and the bass will mostly-cancel. The same thing will happen if you reverse the wires to one speaker.