OK I'm stumped it should work and should not be drawing too much power. Try the GPS device in another system (PC with driver software?).

I do have the shell script (below) that I use to read the interface and extract the GPS time. I use that to se the time on the RPI on power up when there is no network connection otherwise the VRM offline logging goes wrong as the RPi doe not have a battery back up clock.

From the code, it looks like you might be able to

>cat /run/serial-starter/gps/ttyACM0

To see what the GPS device is saying. to the Raspberry pie.

Running the script might give you an idea of what is going on, but without a satellite fix I dont expect it to work.

[Comment the line <date -s $COMMAND> if you don't want to actually touch the RPi date.

Un-comment <echo "$line"> if you want all the data lines from the device.]

#!/bin/bash
N=0;
FILE=/run/serial-starter/gps/ttyACM0
echo "Waiting for GPS data"
while [ ! -e $FILE ] && [ $N -lt 50 ];
do
    sleep 1;
    ((N++))
    echo -n "."
done;
sleep 5;

if [ $N -ge 45 ]; then
   echo " GPS data not available, is the device plugged in?"
   exit 0;
fi

echo
echo "Device attached, waiting for data"

input=$FILE
N=0

# check if GPS has FIX
LINE1='^\$..GGA,[0-9\.]+,[0-9\.]+,[NS],[0-9\.]+,[EW],([0-2])'
# Catch lines with date and time info
LINE2='^\$GPRMC'

FIX=""

# extract date and time from GPS packet

function extract {
[[ $1 =~ ^\$GPRMC,([0-9]{4})([0-9]{2})\.[0-9]{2},.,[0-9\.]+,[NS],[0-9\.]+,[EW],[0-9\.]*,[0-9\.]*,([0-9]{2})([0-9]{2})([0-9]{2}), ]]
  COMMAND="${BASH_REMATCH[5]}${BASH_REMATCH[4]}${BASH_REMATCH[3]}${BASH_REMATCH[1]}.${BASH_REMATCH[2]}"
  date -s $COMMAND
exit 0
}

while IFS= read -r line && [ $N -lt 2000 ] 
do
#  echo "$line"
  [[ $line =~ $LINE1 ]] && FIX=${BASH_REMATCH[1]} && echo "GPS device has a fix after $N lines"
  [[ $line =~ $LINE2 ]] && [[ $FIX -eq 1 ]] && extract $line
  ((N++))
done < "$input"
echo "Timed out no date/time information in 2000 lines from GPS receiver"