This can happen for a few reasons. It can be that you didn't whisk the egg whites enough, you are using a pan that is too wide, making the wrap too big and difficult to flip, or finally, you didn't add enough almond flour. A way to firm up wraps made from egg whites is to add 1/4 teaspoon of xanthan gum to the mixture. It's not easy to dissolve xanthan gum in egg white mixture, so that's why I prefer to make smaller 8-inch wraps and not add any gum as a binder.