Unable to set carrier flow at 500 ml/min

Hello, After having to shut down the lab for the last 7 months (no students) I'm slowly starting the lab up. One of the task was to ensure the lab equipment is working. I have a Shimadzu SSM-5000A (solid module) attached to a TOC-L analyzer. After the initial and routine checks, I tried to start the system up. One of the very first steps is to open the high purity O2 tank and set the carrier gas supply pressure to 44psi . The second step is to set the carrier gas pressure to 200kpa (29ps) using the regulator valve in the SSM-5000a front pannel.  The third step is to set the flow rate for the SSM-5000a to 500mL/min. This is where the problem occurs. It doesn't matter which way I turn the mass flow controller knob the flow gauge does not change from ZERO. I have verified that the gas supply is adequate but I'm at a loss on what is going on. Can anyone help?