SOLVED: So, apparently, InputChanged is fired first, and then added to the textbox, right? So, when I went to string:match, it would match the text BEFORE the new letter was being added. So When you to go match "TACO", it would only match "TAC", because that is what the Text is.

Ok, so I know that there are a lot of reasons why some things work in Client and not in Server, but I don't see how this could be part of that.

local UI = game:GetService("UserInputService")
local TheFlavors = nil
local TheRecipe = nil
local FoundItemName = nil
UI.InputBegan:connect(function(Input,GP)
	if (UI:GetFocusedTextBox()) == TextBox then
		TheFlavors = nil
		TheRecipe = nil
		local Matches = 0

			for MainitemName,Item in pairs (Recipe) do
			if Matches ~= "D" then
				for i,ItemName in pairs (Item.Names) do
					if string.lower(ItemName) == string.lower(TextBox.Text) then
					Matches = "D"
						if Item.Recipe then
						TheRecipe = Item.Recipe
						end
						if Item.Flavors then
						TheFlavors = Item.Flavors
						end
						FoundItemName = MainitemName
						break
					elseif string.lower(ItemName):match(string.lower(TextBox.Text)) then
					Matches = Matches+1
						if Matches == 1 then
							if Item.Recipe then
							TheRecipe = Item.Recipe
							end
							if Item.Flavors then
							TheFlavors = Item.Flavors
							end
						FoundItemName = MainitemName
						end
					end
				end
			end
		if Matches == 0 then
		TextBox.BorderColor3 = Color3.new(156/255, 79/255, 79/255)
		TextBox.Flavors.Visible = false
		TextBox.Recipe.Visible = false
		elseif Matches == 1 or Matches == "D" then
		TextBox.BorderColor3 = Color3.new(82/255, 200/255, 84/255)
			if TheFlavors then
			TextBox.Flavors.Visible = true
			end
			if TheRecipe then
			TextBox.Recipe.Visible = true
			end
		elseif Matches > 1 then
		TextBox.BorderColor3 = Color3.new(15/255,15/255,15/255)
		TextBox.Flavors.Visible = false
		TextBox.Recipe.Visible = false
		end
	end
end
end)

If you type "Taco" in Client, it turns green.

if you type "Taco" in Server, it doesn't work. BUT, if you type "Tacoo" in server, it turns green. WHYYY?