You can try to re-program the chip again, and check whether the error has disappear.
And what the I2C data rate in your tuner tool configure?
You can attached your project, I can try to test it.
I was able to to make it work by creating a new CapSense_Tuner_EZI2C project in a new workspace.
Apparently, something happened in the other project/workspace that prevented me from using the proximity sensor.