You may need to adjust your draw technique. Vaping is not exactly like smoking.
You may need to do some "primer puffs" occassionally to keep the wick/coils saturated. Just suck on the tank without power applied. Thicker e-liquids (with a higher vg content) are not as easily absorbed or moved to the coil, so they need a little assistance with the primer puffs.
This is a common issue with new vapors until they learn how to use their particular device. Not all tanks are created equal, nor are all coils created equal. The Nautilus and Aerotanks have a pretty good reputation if they are the genuine article. However, you may find a different model/brand works better for you if your results continue.
Vaping is a journey to find what works best for you.