AD7172-2 Precision Weigh Scale Issues

I´m using AD7172-2 converter, with external amplifier, in bipolar mode input. The load cell is 30kg capacity and 2mV/V, and the excitation voltage is +5VDC (REF is +5VDC too to do ratiometric system). I attach the scheme.

1- I have configured the Gain of amplier to 426.5 (Rg=470R). When I put about 27-28kg in load cell, AIN1_1 respect to AGND is 0V (it´s saturated). I don´t understand this. I attach table. Any suggestions? Actually, I have configurated the Gain of amplifier to 295.1 (Rg=680R), but I get less points.   

2- What is the procedure to compensate temperature drifts by software, on a weighing scale? Using AD7172-2 with DC excitation of load cell, It generates temperature drifts of the electronic components, which must be compensated, for legal trading, or to meet metrological standards.

Regards.

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