Well certainly you need to make sure that P2.1 has its latch register bit set to '1' to make sure that you can use this pin as an input.

There must be some problem it the circuit that is preventing the ADE7756 chip from being able to pull its output to ground. My gut feel is that your problem is somehow related to one of the following:

- The digital GND is not connected
- The digital VDD has been left open
- The AGND and DGND pins are connected in a way that there is an unaceptable differential voltage between these pins. The abs max spec for this part only allows for +/- 0.3V between these pins.

Hope this helps.
Michael Karas