I see you have found Si Labs AN417 describing the requirements for external oscillator, which I had not looked at before.
I think the best approach would to use an oscilloscope and a low capacitance active probe to check the waveform into the SI4432, after checking the signal from the NOT gates.? I guess worst case is that the SI4432 has been damaged by the initial incorrect connection.? Probably more likely is the divider capacitor value needs some adjustment.
C103/R85/89 in your oscillator circuit - are they needed?? If C103 is kept maybe apply some DC mid point bias to pin 1 of the NOT gate.
What frequencies do you see from the other SI4432?
Dave
