Originally Posted by Dolphyngyrl
Use your fingernails to push fabric around bottom half of grommets really tightly, make sure you are on a hard flat surface. I use both my hands together and push down hard until I hear a faint snap. Sometimes it takes a few times and is frustrating, but once you hear that snap they should not come apart. It helps if the table is lower like a dining room table so you have more leverage. Hope this helps
I do this as well. But I also found, after many bags made for gifts, that it is sometimes necessary for me to trim the fabric edges of the hole I cut a bit closer to my drawn circle so there is not so much bulk inside the grommet. Whenever I have a problem grommet that will not snap shut, thinning the bulk has made all the difference in the world.