If you got them from OSDS, they most likely have a longer prong in the center than most plastic snaps and you'll need to press a lot harder to get it to squish down enough so when you snap, they aren't too high preventing the snap from locking.
If it's just a weak connection that doesn't seem to stay snapped, that's a different problem. I've never had that problem with snaps from Jess, but do have that issue with the snap studs I got from other places. Most likely, you just aren't pressing hard enough. I find a lot of times with the longer prong ones from OSDS, I have to go back and re-press them because I didn't press hard enough the first time.
Try it on a sample piece and see if it helps. I'm not a small gal, and I have to lean a lot of my weight on the press handle to get that little prong squished enough. It's so you can go through thicker fabrics, but when you are doing something thin, it's especially hard to get it squished enough.
Amber
If it's just a weak connection that doesn't seem to stay snapped, that's a different problem. I've never had that problem with snaps from Jess, but do have that issue with the snap studs I got from other places. Most likely, you just aren't pressing hard enough. I find a lot of times with the longer prong ones from OSDS, I have to go back and re-press them because I didn't press hard enough the first time.
Try it on a sample piece and see if it helps. I'm not a small gal, and I have to lean a lot of my weight on the press handle to get that little prong squished enough. It's so you can go through thicker fabrics, but when you are doing something thin, it's especially hard to get it squished enough.
Amber