I designed a load-cell circuit, using AD8226 as instrument amplifier. I connected its power supply to 3.3V. Vref is tied to GND.
It is not working until I change the supply voltage to 5V and above, although the spec specify it needs to work from 2.2V.
You didn't say what the input common mode voltage is, or what the differertial input voltage is,
or what the gain is?? So I can only guess.
Read the InAmp Handbook:
A Designer's Guide to Instrumentation Amplifiers, 3RD Edition, 2006 | Education | Analog Devices
It sounds like you have a diamond plot violation. Use the diamond plot tool:
Instrumentation Amplifier Diamond Plot Tool | Analog Devices