The fabric in the photo above is fraying along the cut circle. The grommet needs a sturdy fabric to hold on to, so if the fabric is fraying (unraveling), the grommet doesn't have anything to securely attach itself to and will pull out.
A few suggestions to try:
- Make the hole smaller, if possible. If your fabric is fairly thin like that shown in the picture, making a small snip with scissors may be sufficient.
- Add a thick stabilizer. (Just adding more layers will help as well.)
- This was mentioned in our FB group: use fabric glue on the edge of the circle and let it dry before attaching the grommet.