Do you use propane or MAPP in that Bernz?
The new low-lead valves are a bit trickier to solder. Clean fitting and tube, ream burr from tube, thin flux application.
Then heat the copper tube outside the fitting until the flux starts to warm and flow, then move the heat to the base of the fitting. Move the flame around the valve, don't keep it in one place.
As soon as the solder melts around the joint, remove the heat or you risk burning the flux.
If the solder is dripping on the floor, the joint is filled, no need to keep melting solder onto the floor. Typically a 1" joint required 1" of solder, same for other sizes 2" fitting 2" of solder.
If you burn the flux, and the solder does not flow into the joint, stop, cool it down, re-clean and re-flux.
Taking most of the lead out of valves and fitting changes the way it solders.
Most often joints fail to solder correctly because they have been over-heated.
Most of the valve manufacturers and the Copper Development Association are releasing You Tube videos on soldering techniques for the new low lead products.
A ball valve should be in the open position when soldering.
This Nibco video is a good one.