The symptoms would suggest that the metal is not getting up to temperature before you move the torch onto the solder.
Keep heating the metal by circling around the joint but NOT on it until the flux goes quite a dark brown and glasssy in appearance. As suggested by metalsmith do this is low light so you can "see" the temperature of the metal. It should be dull red to a "hard" red.
Move the torch closer but NOT on the joint until the temperature seems as described and after another few seconds pass the flame over the solder - it should melt and flow. Do NOT play the torch on to the solder if it doesn't melt - just keep heating around the joint and try again.
If it still fails let it cool off, pickle, wash, clean and re-flux and try again.
Seems like your preparation is good - most important thing is cleanliness of the metal and the solder and suitable flux.
It WILL work with patience and attention to detail.
One last point is you do not say how big the whole piece is, your torch may not be powerful enough if it is a large piece. I am assuming it is a finger ring size if you are using the needlepoint burner.
Barry the Flying Silversmith👍
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