Here is the code:

script.Parent.Activation.OnServerEvent:Connect(function()
    local part = Instance.new("Part")
    part.Size = Vector3.new(1,1,1)
    part.Transparency = 0
    part.CanCollide = false
    
    hitboxActivated = true
    script.Parent.Handle.Touched:Connect(function(hit)
        --NPC
        if hit.Parent:FindFirstChild("Torso") and hitboxActivated == true then
            local torsoPart = hit.Parent:FindFirstChild("Torso")
            hitSFX.Parent = torsoPart
            hitSFX.Volume = 2
            screamSFX.Parent = torsoPart
            hitSFX:Play()
            screamSFX:Play()
            torsoPart.AssemblyLinearVelocity = script.Parent.Handle.CFrame.LookVector * 1500
            hitboxActivated = false
        end
        --PLAYER
        if hit.Parent:FindFirstChild("Torso") and hitboxActivated == true then
            local torsoPart = hit.Parent:FindFirstChild("HumanoidRootPart")
            hitSFX.Parent = torsoPart
            hitSFX.Volume = 2
            screamSFX.Parent = torsoPart
            hitSFX:Play()
            screamSFX:Play()
            
            part.Position = torsoPart.Position
            part.AssemblyLinearVelocity = script.Parent.Handle.CFrame.LookVector * 100
            part.Parent = torsoPart
            
            local weld = Instance.new("WeldConstraint")
            weld.Part0 = part
            weld.Part1 = torsoPart
            
            hitboxActivated = false
        end
    end)
    wait(3)
    hitboxActivated = false
end)

Whenever I test the tool in game, it doesn’t apply the force onto the hit player. It just does

AssemblyLinearVelocity = 0,0,-0

I have tried multiple ways to try and fix, but still no luck. Does anybody know how to fix this problem?