No wifi connections showing, home button stopped working

I'm curious as to what problem you were trying to address by simply melting some flux on the NAND.

The first thing that comes to mind is insuring that the interconnect cable, on the back of the logic board, was re-installed or not damaged. Whenever you apply heat to a logic board, even low heat, you always run the risk of collateral damage. If you "take you time" what you are really doing is applying more heat. Eventually, parts can become dislodged, get bridged with adjacent parts or simply blown away. You also have to consider that sometimes the damage happens on the reverse side, where gravity encourages components to "fall" off the board.

There's not really enough information to give a precise diagnostic but I would do a thorough visual inspection, preferably with magnification and then focus on the two subsystems and their related circuitry to see if anything is obviously wrong. After that, you need to start probing the circuits.