You know like the kind that go on a window or bathroom mirror or on the wall or in the shower. They need the atmosphere pushing down on them to work, right?
Yes. They won't work because they operate on a difference in air pressure providing a force. No air? No force. Same reason an airplane wing won't provide lift in the upper atmosphere.
But, compare to a rocket engine that does NOT need an atmosphere to push against.
I like the gauge block notion. A (quick) search says that it's a combination of surface tension from the oils they're coated in, suction (gone for us), and the super flat surfaces slightly exchanging electrons and bonding in close proximity.
I'm a fan of the surface tension angle as the "rocket of suction cups", since it's got that "non-binding force" element, where welding or glue feels different, and Velcro feels like a tangle.
It's "pull-y" where suction is "push-y".
Now the question is would surface tension grab something in a vacuum the way it does outside of one. I know you'd have water sublimate off, so it's questionable to me.