Are you referring to playlists you manually sync between your devices and iPad (though iTunes on a Pc), or playlists linked to your Apple Music Account?
If your case falls in the former category, than you may have problems syncing the tracks on your iPad. Make sure all tracks are present on your Pc, and that during syncing, no error message pop up appears. Also, if music in your playlists is flagged as explicit, make sure your iPad does allow explicit content in tracks in its Restriction section of Settings; if it is not allowed, explicit music will actually be copied on the device, but will be basically inaccessible until the Explicit content is consented