I apologize if this is obvious, but on a new version of a MSP430FR5949 based datalogger programmed using Energia 18 - I switched the pins on the physical chip for serial communication from the Aux to the Debug UART for better layout. Below is the modified pin map energia_pins.h file -
#if defined(__MSP430_HAS_EUSCI_A0__) || defined(__MSP430_HAS_EUSCI_A1__)
static const uint8_t DEBUG_UARTRXD = 18; /* Receive Data (RXD) at P2.1 */
static const uint8_t DEBUG_UARTTXD = 17; /* Transmit Data (TXD) at P2.0 */
static const uint8_t AUX_UARTRXD = 22; /* Receive Data (RXD) at P4.5 */
static