INA122p replace to INA126p
The INA126 does not have the same capabilities as the INA122. The 122 can work with input signals that swing as low as the most negative rail of the device which, in your example, appears to be 0V. The 126 has problems in this respect: -



I've circled the bit that shows the common mode input range when on a 5V/0V supply. Two things to note - the input range only goes down to about +1V and the output can only swing as low as about 0.6 volts. Here's the 122 equivalent picture: -



The input range includes 0 volts and the output looks like it will swing down to below 100 mV.