I am sure you have tried this , but I shall offer the wisdom and tidbits that have helped me in the past with a great many lighters.
Purge , purge , purge the lighter of all of the butane! Take a pick or some object that will allow you to depress the fill orfice on the bottom of the lighter and let all the butane gas out. Also a piece of tape over the lever to depress will hold it down and let all the gas vent out. Then after you think all the gas is out of the lighter depress the lever a few more times and listen for gas escaping. If there is no gas in it then refill with some quality butane triple or quad filtered. Press the canister onto the fill orfice and depress , but do not let up and press it on again. It needs to be pressed onto the fill orfice and held and only released when a full fill has been obtained so hold it there for a while.
Then allow the lighter to aclimate to room temperature and try to ignite once again.
I also use isopropyl alcohol on a swab to gently clean the nozzle where the gas is directed from if the first tip does not have success. Be careful though as to not damage or move the electrode tip that provides the spark.
Hope this helps!