Yep. Have to turn the lights on. All military vehicle start out in "light discipline" mode. You don't even get blackout drive unless you select it. On the pushbutton switch you press any button to wake it up and then your desired mode and enter.
If you have service drive turned on and they still don't work.... Clean every ground in the truck (there's over 100), replace all the old style circuit breakers with blade fuses, replace all the relays with appropriate NEW 12v or 24v five pin relays and then report back results.
Turn signal stalks do fail. Have seen that multiple times. Also the pushbutton switches on the A1+ trucks can and do fail - usually because they have a poor ground either at their dedicated ground wire (lever switch does not have) or the PDP ground in the passenger grab handle or the cab ground behind the radiator (particularly naughty) or one of the MANY other grounds that likely need serviced badly.