LP-MSP430FR2476: Trouble communicating via I2C with LP5569

I am having trouble establishing multi-byte, interrupt-driven I2C communication from my MSP430FR2476 (master) to my LP5569 (slave) LED driver. I have followed the examples to setup some skeleton code, and I just want to write two bytes to the LP5569. Namely, I need to send it a control register address, and data to write to that control register. I am using 0x40 for the value of the slave address.

Here is a rough sketch of what I am trying to do:

#include "driverlib.h"
#include <msp430fr2476.h>

#define SLAVE_ADDRESS 0x40


// Pointer to TX data
uint8_t TXData = 0;
uint8_t TXByteCtr;

void main(void)
{
    WDT_A_hold(WDT_A_BASE);

    // Configure Pins for I2C
    GPIO_setAsPeripheralModuleFunctionInputPin(
        GPIO_PORT_P1,
        GPIO_PIN2 + GPIO_PIN3,
        GPIO_PRIMARY_MODULE_FUNCTION
    );

    /*
     * Disable the GPIO power-on default high-impedance mode to activate
     * previously configured port settings
     */
    PMM_unlockLPM5();

    EUSCI_B_I2C_initMasterParam param = {0};
    param.selectClockSource = EUSCI_B_I2C_CLOCKSOURCE_SMCLK;
    param.i2cClk = CS_getSMCLK();
    param.dataRate = EUSCI_B_I2C_SET_DATA_RATE_400KBPS;
    param.byteCounterThreshold = 0;
    param.autoSTOPGeneration = EUSCI_B_I2C_NO_AUTO_STOP;
    EUSCI_B_I2C_initMaster(EUSCI_B0_BASE, &param);

    //Specify slave address
    EUSCI_B_I2C_setSlaveAddress(EUSCI_B0_BASE,
            SLAVE_ADDRESS
            );

    //Set Master in receive mode
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE,
            EUSCI_B_I2C_TRANSMIT_MODE
            );

    //Enable I2C Module to start operations
    EUSCI_B_I2C_enable(EUSCI_B0_BASE);

    EUSCI_B_I2C_clearInterrupt(EUSCI_B0_BASE,
            EUSCI_B_I2C_TRANSMIT_INTERRUPT0 +
            EUSCI_B_I2C_NAK_INTERRUPT
            );
    //Enable master Receive interrupt
    EUSCI_B_I2C_enableInterrupt(EUSCI_B0_BASE,
            EUSCI_B_I2C_TRANSMIT_INTERRUPT0 +
            EUSCI_B_I2C_NAK_INTERRUPT
            );
    EUSCI_B_I2C_masterSendMultiByteStart(EUSCI_B0_BASE, 0x40);
    for(;;)
}

//------------------------------------------------------------------------------
// The USCIAB0TX_ISR is structured such that it can be used to transmit any
// number of bytes by pre-loading TXByteCtr with the byte count. Also, TXData
// points to the next byte to transmit.
//------------------------------------------------------------------------------
#pragma vector=USCI_B0_VECTOR
__interrupt void USCIB0_ISR(void)
{
    switch(__even_in_range(UCB0IV, USCI_I2C_UCBIT9IFG))
  {
        case USCI_NONE:             // No interrupts break;
            break;
        case USCI_I2C_UCALIFG:      // Arbitration lost
            break;
        case USCI_I2C_UCNACKIFG:    // NAK received (master only)
            //resend start if NACK
            EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);
            break;
        case USCI_I2C_UCTXIFG0:     // TXIFG0
            // Check TX byte counter
            // Not reaching this point
            EUSCI_B_I2C_masterSendNextByte(EUSCI_B0_BASE, 0x40);
            break;
        default:
            break;
  }
}

The code hangs before it gets to any interrupt code. Within the multi-byte start call in eusci_b_i2c.c, the program hangs on the following line in EUSCI_B_I2C_masterSendMultiByteStart():

//Poll for transmit interrupt flag.
while (!(HWREG16(baseAddress + OFS_UCBxIFG) & UCTXIFG)) ;

I am also curious about what the best way to troubleshoot this problem is. I am following the driverlib's User Guide to configure the I2C module, and the GPIO pins are definitely setup properly. I have been walking through the program, and it looks like all the interrupt flags are set up properly. Any advice is greatly appreciated! Thanks in advance.