Since the contents in your oil pen cartridge can potentially vary in viscosity and because viscosity can vary due to temperature, elevation, air pressure, and contact with direct sunlight or heat, it is possible that your Galactic Oil Pen Cartridge can get clogged between uses or by being stored too long in various conditions. In general, a couple of strong tokes can clear a clog, either with the cartridge attached to the battery or sometimes better with the cartridge separated for maximum air flow.
However, if that isn’t working, the next best option is to add heat to the mix. A hair dryer or car/home heating vent may give you the fastest results. Simply blow hot air at the contents of the cartridge from all sides, evenly. As the liquid becomes more viscous, take a couple of tokes and the clog should clear right up. This will also increase air flow as the liquid is able to soak the wick and flow into the atomizer chamber. Another option is to position the oil vape next to a car/home heating vent and use the hot air from that, making sure to heat evenly.
Caution: Too much heat too fast can warp the cartridge and potentially burn you, so be very cautious not to use too much heat for too long, and avoid touching the hot metal portion of the device. Also, if your cartridge is not attached to the battery or does not have the storage cap attached, too much heat may cause a leak.