Do the caps not go off at all, even after dropping the hammer on them a couple of times? If the go off after a couple tries you may a problem with cap fitting properly on the nipple.
If the caps don’t go off at all, check that the disk that holds the explosive charge didn’t fall out of the. Had some Remington caps not that long ago and noticed some little green disks in the tin. You could tap the caps on a hard surface and the charge would come out. Only had this issue with one tin, but suspected entire lot could be questionable. Emailed Remington, but never heard back.