CCS/MSP430F5529: Can't get UART0 interrupt to trigger

Tool/software: Code Composer Studio

I've spent an entire day just trying to get UART0 RX to trigger an interrupt with no luck. I am able to get UART1 RX to trigger, and I am able to TX on both UART0 and UART1. I've tried swapping the RX lines (P3.4 & 4.5) and I get the same results (ie. triggering on UART1 but not on UART0) so it doesn't seem like it's my serial hardware or terminal that's the issue.

Can someone please take a look to see if something is obviously wrong with my code? This is the latest iteration that has been cleaned up. 

#include <msp430.h>


int main(void) {
    WDTCTL = WDTPW | WDTHOLD;   // Stop watchdog timer

    //SETUP UART0
    P3SEL    |= BIT3 + BIT4;                    // P3.3,4 = USCI_A0 TXD/RXD
    UCA0CTL1 |= UCSWRST;                        // **Put state machine in reset**
    UCA0CTL1 |= UCSSEL_1;                       // CLK = ACLK
    UCA0BR0 = 0x03;                             // 32kHz/9600=3.41 (see User's Guide)
    UCA0BR1 = 0x00;                             //
    UCA0MCTL |= UCBRS_3+UCBRF_0;                // Modulation UCBRSx=3, UCBRFx=0
    UCA0CTL1 &= ~UCSWRST;                       // **Initialize USCI state machine**
    UCA0IE |= UCRXIE;                           // Enable USCI_A0 RX interrupt

    // set up UART1
    P4SEL    |= BIT5 + BIT4;                    // USCI_A1 TXD/RXD
    UCA1CTL1 |= UCSWRST;                        // **Put state machine in reset**
    UCA1CTL1 |= UCSSEL_1;                       // CLK = ACLK
    UCA1BR0 = 0x03;                             // 32kHz/9600=3.41 (see User's Guide)
    UCA1BR1 = 0x00;                             //
    UCA1MCTL = UCBRS_3+UCBRF_0;                 // Modulation UCBRSx=3, UCBRFx=0
    UCA1CTL1 &= ~UCSWRST;                       // Initialize USCI state machine
    UCA1IE |= UCRXIE;                           // Enable USCI_A1 RX interrupt


    // Push button
    P1DIR |= BIT0;                              // Set P1.0 to output direction
    P1OUT &= ~BIT0;

    P1REN |= BIT1;                              // Enable P1.1 internal resistance
    P1OUT |= BIT1;                              // Set P1.1 as pull-Up resistance
    P1IES &= ~BIT1;                             // P1.1 Lo/Hi edge
    P1IFG &= ~BIT1;                             // P1.1 IFG cleared
    P1IE |= BIT1;                               // P1.1 interrupt enabled

    __bis_SR_register(LPM3_bits + GIE);         // Enter LPM0, interrupts enabled
    __no_operation();                           // For debugger

}

//Echo back RXed character, confirm TX buffer is ready first
// APP UART
#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
{
    // This interrupt is never entered
    switch (__even_in_range(UCA0IV, 4)) {
    case 0:     break;
    case 2:
        while(!(UCA0IFG&UCTXIFG));
        UCA0TXBUF = UCA0RXBUF;
        break;
    case 4:     break;
    default:    break;
    }
}

//Echo back RXed character, confirm TX buffer is ready first
// APP UART
#pragma vector=USCI_A1_VECTOR
__interrupt void USCI_A1_ISR(void)
{
    // This triggers on UART1
    switch (__even_in_range(UCA1IV, 4)) {
    case 0:     break;
    case 2:
        while(!(UCA1IFG&UCTXIFG));
        UCA1TXBUF = UCA1RXBUF;
        break;
    case 4:     break;
    default:    break;
    }
}

// Port 1 interrupt service routine
#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void)
{
    switch( __even_in_range( P1IV, P1IV_P1IFG7 )) {
    case P1IV_P1IFG1:                                       // Pin 1 (button 2)
        P1OUT^=BIT0;
        UCA0TXBUF = 0x22;       // This generates output on UART0
        UCA1TXBUF = 0x33;       // This generates output on UART1
        break;
    default:   _never_executed();

    }

}