SSD won't mount when plugged in

I have a SANDISK 960GB ULTRA II SSD3.0GB/S. Should this drive mount without power? I can’t seem to get it to work without power, that is, power through USB port doesn’t do the trick. Any recommendations on enclosures that allow this? Currenlty in an unpowered enclousre and no luck.

I’m connecting this to a Mac and I have no trouble using a drive adapter which is powered.

Thanx in advance,