MSP430FR2155: After entering low power mode LPM4, the chip freezes

Hey Leo,

I think you may be missing this:

    // Disable the GPIO power-on default high-impedance mode
    // to activate previously configured port settings
    PM5CTL0 &= ~LOCKLPM5;

Here is a GPIO interrupt example for another FRxx device.  https://dev.ti.com/tirex/explore/node?node=A__ADK3rB2bf-DOgn6aSbCoTQ__msp430ware__IOGqZri__LATEST 

Hope this helps.  

JD