Trouble setting up blueprints for First Person variable movement speed

It does look like your blueprint should work fine, maybe your InputAction isn’t set up correctly?

Since you’re using the movement component, you could have one less function and only increase the Movement Components Max Speed

( Mouse Wheel Axis gives you 1.0 or -1.0 )
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We are adjusting the Max Speed by +1.0 or -1.0 from the Axis Values, if you want a faster rate of change, just multiply the Adjust Speed before adding it.

This way you won’t need the Adjust Move Forward function, hopefully, this is of use to you.