How can I solve this error which does not seem to make sense?

Hi,

Output is saying "Stem_Cell is not a valid member of Configuration Script 'Workspace.Cell.ChangeScript', Line 8 stack end," however the script does not refer to Stem_Cell being in Configuration. The script is below. The hierarchy is here. Can anybody see what the problem is? Thanks.

while true do
        wait(0.1)
        if script.Parent.Configuration.Heart.Value == true then
                script.Parent.Stem_Cell.Transparency = 1
                script.Parent.Heart.Transparency = 0
                for _,v in pairs(script.Parent.Nerve_Cell:GetChildren()) do
        if v:IsA("Part") then
            v.Transparency = 1
                end
end
        else if
                script.Parent.Configuration["Nerve Cell"].Value == true then
        game.Workspace.StoryValues.IsNerveCellGrowing = true
                script.Parent.Stem_Cell.Transparency = 1
                script.Parent.Heart.Transparency = 1
for _,v in pairs(script.Parent.Nerve_Cell:GetChildren()) do
        if v:IsA("Part") then
                v.Transparency = 0
        end
        game.Workspace.StoryValues.IsNerveCellGrowing = false
        game.Workspace.StoryValues.HasNerveCellGrown = true
end
        else
                script.Parent.Stem_Cell.Transparency = 0
                script.Parent.Heart.Transparency = 1
                for _,v in pairs(script.Parent.Nerve_Cell:GetChildren()) do
        if v:IsA("Part") then
                v.Transparency = 1
        end
        game.Workspace.StoryValues.IsStemCellPresent.Value = true
        game.Workspace.StoryValues.IsNerveCellGrowing.Value = false
                        end
                end
        end
end