AX-12A not functioning with Arduino Uno and Shield

I am having an issue getting the AX-12A servo to work. I am using an Arduino Uno, the Dynamixel Shield, and an external 12 V supply. I am trying to run the sample program “position_mode” from the library. The jumper J2 is removed since the supply voltage is connected to the green connector JP9. The servo is connected to the J5 TTL connector. When uploading the Arduino program, SW1 is off and SW2 is set to “upload.” In the program itself, (line 56) DXL_ID = 1; (line 57) DXL_PROTOCOL_VERSION = 1.0;
(line 72) dxl.begin(1000000).

Both protocol versions have been tried. The Baud rate hasn’t been changed from the default.
When switching to “Dynamixel” on SW2 and then turning on SW1, the red light on the servo flashes once but the servo does not turn. The pin connections have been referenced against the data sheets and verified.

Different servos have been used and tested with the same results. Multiple example and original programs have been used with no rotation seen at the servo.

Are there any other factors to consider, perhaps in the software or connections that haven’t been done already that would otherwise prevent the servo from turning?
Roboplus is installed and I have tried to use the terminal to view scan_dynamixel results but the com ports are busy. If there are any tips to running the scan as well that would be helpful.