I typically confirm commands with a right-mouse-button-click. _vSaveVol needs two before it reacts:
Command: _vSaveVol Select volume objects <I do that and click rmb> Select volume objects <another (useless) rmb>
NB: I only have one vVolume (a vUnion of a vSphere and a vBox) in my scene.
RE: _vSaveVol - Added by Turlif . over 7 years ago
This of course should not be the case. Looks like I am not able to repeat this bug on my end with the file from your other post, however I have sent it to QA for more testing.