I empty mine the turn it upside down then attach the refill can. Many lighters can be finicky with different fuels and you didn't specify if it's not lighting after fueling or if it's not fueling. I have had lighters leak thru the jests after fueling that's a lighter problem. If it leaks out the fuel hole that could be clogged or dirty. Not sure how easy that would be to clean. If they have windows you should see how full they are granted a completely full won't have an air bubble yet. I think it is recommended not to shake refuel can before fueling.

After refilling the lighter adjustment needs to be lowered as you probably had to turn it up as fuel pressure drops as there is more space in fuel cell after using. Too much pressure can blow your flame out