From my experience on previous repairs and also from what I have learned from Chris Long videos, If *#06# does not display the IMEI, it is Baseband. First, check well for short on caps around baseband, if not any...run jumpers on U1 and V1...
Just reflowing the IC will not be enough for this type of repair. As Chris Long explains in his Iphone 6 Plus "No Service" repair, you will need to remove shield, remove Baseband, Reball, Clean pads, and run 2 jumpers to the U1 and the V1 pads. (Much like the M1 Meson U2402 jumper).
Although you can also run short jumpers (Which do not last as long), it is recommended to remove the Sim slot and run the "Long jumpers".
Go watch a video from Chris (Starts at about 3:55:00 that gives a full explanation and the process for this repair, as well as other things that can cause this issue.