Configuring input on MSP430?
As OP has noted in the comments, issue was due to code changing the state of the Port 1 Output P1OUT. When PxREN is enabled for a given port and pin, the corresponding bit for the same port and pin in PxOUT controls whether the builtin Pull-Up (Logic 1) or Pull-Down (Logic 0) is connected. PxDIR must also be set to Logic 0 for the port and pin to be an input.

Consequently, Op had set the P1.1 Button Input to pull-down to Gnd, when the button is also tied to Gnd when pressed.