attempt to index nil with 'Text' fix?

local frame = script.Parent
local textBox = script.Parent
local open = workspace.openPart
local close = workspace.closePart
local closeBtn = frame.CloseButton
local Players = game:GetService("Players")
local localPlayer = Players.LocalPlayer
local Gold = localPlayer.leaderstats.Gold
local errorGui = localPlayer.PlayerGui:WaitForChild("ErrorGui")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local remoteEvent = ReplicatedStorage.buySeeds

frame.Visible = false
errorGui.Enabled = false

local price = {
	['Wheat'] = 100, 
	['Corn'] = 250, 
	['Rice'] = 2000, 
	['Bamboo'] = 8400, 
	['Soybean'] = 24000, 
	['Cabbage'] = 57600, 
	['Carrot'] = 85000, 
	['Potato'] = 120000
}

for _,UI in pairs(script.Parent:GetDescendants()) do
	if UI:IsA('TextButton') then
		UI.MouseButton1Click:Connect(function(ItemName, player)
			local AmountPurchase = tonumber(UI.Parent:FindFirstChildOfClass('TextBox').Text)
			local Seed = UI.Parent:FindFirstChildOfClass('TextBox').Name:gsub('BuyAmount','')
			--Loops through how many times you entered in the box to purchase
			if AmountPurchase then
				for i=1,AmountPurchase do
					print(Gold.Value, price[Seed])
					if Gold.Value >= price[Seed] then
						Gold.Value -= price[Seed]
						remoteEvent:FireServer(Seed.Name)
						print("Successfully Purchased")
					elseif Gold.Value < price[Seed] then
						print("Insufficient Funds")
						errorGui.Enabled = true
					end
				end
			end
		end)
	end
end

local function openMenu(otherPart)
	frame.Visible = true
		local player = Players:GetPlayerFromCharacter(otherPart.Parent)
		if player.Name == localPlayer.Name then
			localPlayer.Character.Humanoid.WalkSpeed = 0
		end
	end

local function closeMenu()
	frame.Visible = false
	localPlayer.Character.HumanoidRootPart.CFrame = CFrame.new(
		close.Position.X, close.Position.Y + 3, close.Position.Z)
	localPlayer.Character.Humanoid.WalkSpeed = 16
end

open.Touched:Connect(openMenu)
closeBtn.MouseButton1Click:Connect(closeMenu)

your using :GetDescendants() which mgiht find stuff that isn't parented to the same parent as the textbox, try adding an if statement to see if it finds it