Hi,
The Action will only work for the build in unity input.
I did not know you are using rewired
The Horizontal axis and Vertical Axis are string variables to get the name from the input where the action should get the value from the input manager from unity.
You are probably using playmaker 1.9 as you could place the values in the action.
which in this case, convert your float value into a string value and looks in the input manager for that string name.
But no worriesI made a custom version from the action which you can feed the float variables now
so this could work with any 3rd party input control.
I won't place it yet on the ecosystem (i will to some more testing) but you can get it from the attachment below.
Let me know if it worked.