Here are some common issues as well as potential solutions
If these answers do not work then feel free to make a post on the subreddit which is found at the bottom of all pages on this site.
There are a few common causes of clogs like the coil getting flooded due to getting too hot. Another cause is the airway going into the mouthpiece of the device will slowly collect reclaim from the vapor and will eventually clog the device if it's not regularly cleaned. The final common cause is taking too short of a hit, especially with the GT Ccells as a 1-2 second hit won't fully vaporize the wicked oils while still wicking more if enough hits are taken back to back.
There are a few methods for this, the easiest but riskiest is just holding the fire button for a few seconds while sucking on it, the warmth will warm up the oil enough to melt it however this usually results in hot oil in your mouth which isn't fun. The next easiest is using a toothpick or dab tool to scrape out the oil inside, be careful when getting close to the ceramic as it's brittle and can crack if you try to scrape the coil itself. Another method is warming up the tank/pod and setting it upside down to drain out, though you'll want to do this when the tank is low otherwise it could continue wicking and purge a lot of the tank. If you want to re-use the oil that was pulled out you can do so but it will likely be similar to smoking reclaim from a dab rig, you'll also want to make sure it's not dusty since dust will likely settle in the sticky mouthpiece.
The most common reason for this is using your device at too high of a wattage, the "recommended wattage" on many of these coils is too high for this use case and you need to use a lower wattage. The Nord & PnP ceramic coils as well as the RPM Quartz coils run well at 3-8w, I usually run them at 5w. The 0.5ohm GT Ccell runs well at 15-20w in wattage mode or 20-30w in Temperature Control (TC) mode at 350-420F (175-215C), the 0.3ohm GT Ccell usually needs 5-10w more. Other reasons could be that you didn't properly wick the coil and may need to wait for it to slowly wick or your airflow is too cut off as too little airflow can make it taste worse or hit more harshly.