Lots of possibilties.
You should be heating the cleaned and fluxed joint itself on all sides as much as possible.
Should take no more than 30 seconds before it sucks the solder up into the joint.
You do not need to feed the joint solder until it's running and dripping on eveything.
If the torch is of sufficient capacity and the flame shape is correct as in forcefull and pointy.
If there is no water whatsoever in the the joint.
Applies to all solder joints.