I use the 3m technique. Pinch the ends and press them inside the ear canal and apply light pressure to the ends so they don't pop out. The foam takes long time to go back in shape like a minute. Sometimes they don't go back in shape so i bend it at top a bit and press it in my ears. My ear canals are big so these come off sometimes.Can you describe how you are inserting them?
I've been using the 3M earplugs for more than a decade now. Can even sleep with them on.