Your stamps do definitely work, as you can see from the original test print I made on your storage box or paper bag. But rubber stamping does take some practice.
Please try the following:
1) Ensure your ink pad is being thoroughly inked. No need to press the ink down hard, that can actually cause more issues by flooding ink into the negative spaces. Just lay your stamp face upon your table, and tap the ink down on it lightly several times to get even coverage. You can check in the light to ensure that there is a nice wet sheen over the whole stamp :)
2) Place your stamp on your desired paper. Note, paper and cardstock are the best, a very thin corrugated box (like the SlotBox that logo and portrait stamps are shipped in), but a regular corrugated box will not take a good imprint because of the empty space in the corrugation. All surfaces must be FLAT ... so no assembled boxes or anything with bumps. And ensure that there is nothing under your paper/card.
3) With large stamps (ie anything over 2"), it's best to apply pressure by standing up and pushing down, its much harder to get a perfect imprint by sitting.
4) Apply pressure first to the centre, then, keeping the stamp very still, apply pressure to the four sides. And for good measure I always apply pressure to the centre again. It's important that the stamp doesn't move, so use your other hand to steady it while you re-adjust your pressure.
5) Practice. Make sure to get some solid imprints on some test paper before moving on to product or expensive bags and boxes.
I know this seems like a lot of steps, but truly it took me all of 5 seconds to stamp your box/paper bag, and you can see examples of that in my carving/stamping videos on my insta @saltandpaperca