I have tried using the different buttons to control the movement. SPRINT, USE, DUCK ect. None of them appear to be working. I tried creating permissions also and assigning them incase that was the cause, but no change. 

I solved my issue. I had changed the "Move Frequency": 0.2 to 100. Changing it back to 0.2 and increasing the "Speed Modifier" to 1800 has resolved my issue. 

This is my config file for reference.

{
"Speed Modifiers": [
{
"Permission": "",
"Speed Modifier": 1800.0
}
],
"Move Button": "SPRINT",
"Disable Wind Force": true,
"Move Frequency": 0.2
}