Thanks I tried using your 2) suggestion

Use CONSEQ=1 and MSC=1

The updated code is

#include "msp.h"

uint16_t resultsBuffer[2];

void main(void){

    WDT_A->CTL = WDT_A_CTL_PW | WDT_A_CTL_HOLD;

    P5->SEL1 |= BIT5 | BIT4; // Set P5.5 as ADC input A0 and P5.4 as ADC input A1
    P5->SEL0 |= BIT5 | BIT4; // Set P5.5 as ADC input A0 and P5.4 as ADC input A1

    // initialize P1.0  for Output
    P1->DIR  |= 0b00000001;  // Set P1.0 Output pin
    P1->OUT  &= ~1;          /* turn off P1.0 */

    // initialize P2.4 and make it a timer output
    P2->DIR  |= 0b00010000;  // Set P2.4 as an Output pin
    P2->SEL0 |= 0b00010000;  // Set P2.4 as Primary function Timer_A0_C1  CCR0 Output

    // initialize P4.2 and make it a timer output
    P4->DIR  |= 0b00000100;  // Set P4.2 as an Output pin
    P4->SEL0 |= 0b00000100;  // Set P4.2 as Primary function ACLK

    CS->KEY = CS_KEY_VAL;
    CS->CTL1 |= CS_CTL1_SELA_2;
    CS->KEY = 0;

    ADC14->CTL0 &= ~ADC14_CTL0_ENC; // Reset ENC bit for configuration
    //Timer_A0 output 1 trigger, Sampling timer is the source of sampling signal, multi channel-repeated conversion mode, Sample and hold time is 8 ADC clock cycles, ADC14 on

//    ADC14->CTL0 = ADC14_CTL0_SHS_1 | ADC14_CTL0_SHP | ADC14_CTL0_CONSEQ_3 | ADC14_CTL0_SHT0_1 | ADC14_CTL0_ON;

    ADC14->CTL0 = ADC14_CTL0_SHS_1 | ADC14_CTL0_SHP | ADC14_CTL0_CONSEQ_1 | ADC14_CTL0_SHT0_1 | ADC14_CTL0_ON | ADC14_CTL0_MSC;

    ADC14->MCTL[0] = ADC14_MCTLN_VRSEL_0 | ADC14_MCTLN_INCH_0; // Vcc - Vss references, input channel A0, End of sequence
    ADC14->MCTL[1] = ADC14_MCTLN_VRSEL_0 | ADC14_MCTLN_INCH_1 | ADC14_MCTLN_EOS; // Vcc - Vss references, input channel A1, End of sequence
    ADC14->IER0 = ADC14_IER0_IE1; // ADC interrupt enabled for ADC14->MEM[1]

    ADC14->CTL0 |= ADC14_CTL0_ENC; // Start conversion-software trigger

    TIMER_A0->CCR[0] = 42;  // PWM period
    TIMER_A0->CCR[1] = 4; // CCR1 PWM duty cycle
    TIMER_A0->CCTL[1] = TIMER_A_CCTLN_OUTMOD_6; // CCR1 set/reset
    TIMER_A0->CTL = TIMER_A_CTL_TASSEL_1 | TIMER_A_CTL_MC_1 |  TIMER_A_CTL_CLR; // ACLK, Up mode, Clear TAR

    NVIC->ISER[0] = 0x01000000; // ADC14 interrupt is enabled in NVIC
    __enable_irq(); // All interrupts are enabled

    SCB->SCR |= SCB_SCR_SLEEPONEXIT_Msk; // Sleep on exit
    __sleep(); // enter LPM0
}

// ADC14 interrupt service routine
void ADC14_IRQHandler(void){
        P1->OUT |= 1;             /* turn on P1.0 */
        ADC14->CTL0 &= ~ADC14_CTL0_ENC; // Reset ENC bit for configuration
        if (ADC14->IFGR0 & ADC14_IFGR0_IFG1){
        resultsBuffer[0] = ADC14->MEM[0];
        resultsBuffer[1] = ADC14->MEM[1];
        P1->OUT &= ~1;            /* turn off P1.0 */
        ADC14->CTL0 |= ADC14_CTL0_ENC; // Start conversion-software trigger
        __no_operation();}
}

Now the ADC ISR is happening on every Timer trigger.

See scope shot below

CH1 is the Timer A0_1 out which is the ADC trigger source and CH2 is an output bit togged on and off inside the ADC ISR.

The code I posted has been modified a lot from the original, but to give credit to the original example, it came from

the Book: Programmable Microcontrollers: Application On The MSP432 LaunchPad.  Starting Example code was Listing 8.10