the absolute maximum input powers are:
RF Input +8 dBm, LO +10 dBm. Voltages +4.5 volts. IF you exceeded those in initial testing you very well could have blown out the chip.
IS it taking 160 mA approximately from the DC power supply,as it should be?
Time to reflow a new chip on there and see if it starts to work.
Also you could post the layout artwork you are using for both sides of the board, and we can see if there is something obviously wrong
Also: "pins 2, 4, 10, 12, 17, 19, 21 These pins and the exposed ground paddle must be connected to RF/DC ground"
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another idea: look at the IF output to make sure the chip is not oscillating due to poor layout.