Hi, Eric. It's a little harder to tell exactly what is going on without seeing it, but it sounds like you may not be getting the housing hot enough. The small tube is probably taking the heat very easily and the housing needs a LOT more heat before it is ready to accept or melt solder.
As far as where to go from here, the tube could be soldered in at the factory before a lot of heat could cause a problem in finish. Or, heavy heat now could ruin the piece. Knowing this, if you want to try heating the housing longer, and preferably with MAPP gas, you MIGHT be able to get the solder to melt on both pieces--or you might end up with an unusable wad. I do believe that I would try to get a lot of heat into the housing before I inserted the tube as too much heat could melt the tube and the tube will accept heat easily. The bottom line is that you can try it but be prepared to replace the assembly if problems occur.