Some oils are thicker than other and we use different dripper inserts for some oils, however, if they are cold they may be slower to drip out of the bottle. Try warming your bottle of oil up in your hands or pocket (don't use hot water or anything else) and then, without shaking the bottle just tip fully up and hold, the air will take a little while to enter the bottle to displace the oil but it will happen, just give it a little longer.