Tree Farm stuck in loop

Today I wrote a script for a small tree farm to learn some lua basics and now it is stuck in a loop and I cannot figure out why.
The code is meant to run a tree farm that consists of a turtle with a sapling on 3 of its 4 sides, an enderchest beneath it, and an openblocks vacuum hopper on the side that does not have a sapling. There is a different enderchest in slot 15 that has charcoal in it and slot 16 holds saplings.

--ItemSort
local function itemsort()
  local n = 1
  while n < 15 do
	turtle.select(n)
	local item = turtle.getItemDetail()
	if item then
	  print(item.name)
	  if
		item.name == "minecraft:sapling"
	  then
		turtle.transferTo(16)
	  else
		turtle.dropDown()
	  end
	  n = n + 1
	else
	  n = n + 1
	end
  end
end

--Dig a Tree
local function tree()
  turtle.dig()
  turtle.forward()
  repeat
	turtle.digUp()
	turtle.up()
  until turtle.digUp() == false
  repeat
	turtle.down()
  until turtle.down() == false
  turtle.back()
  sleep(5)
  itemsort()
  turtle.select(16)
  turtle.place()
end

--Refuel from Enderchest
local function chestfuel()
  itemsort()
  end
  print("Checking Fuel Level")
  if turtle.getFuelLevel() < 30 then
	print("Refueling")
	turtle.select(15)
	turtle.placeUp()
	turtle.suckUp()
	turtle.select(1)
	turtle.refuel()
	turtle.select(15)
	turtle.digUp()
  else
	print("Good Enough")
end

--Main Script
while true do
  turtle.select(1)
  local success, front = turtle.inspect()
  if success then
	if
	  front.name == "minecraft:log"
	then
	  tree()
	  end
	elseif
	  front.name == "minecraft:sapling"
	then
	  turtle.turnLeft()
	else
	  turtle.turnLeft()
  end
  chestfuel()
end

The only thing I can find wrong/strange with your code is your chestfuel function,

local function chestfuel()
  itemsort()
  end --#end declaration of function
  --#everything below is not within the chestfuel() function
  print("Checking Fuel Level")
  if turtle.getFuelLevel() < 30 then
        print("Refueling")
        turtle.select(15)
        turtle.placeUp()
        turtle.suckUp()
        turtle.select(1)
        turtle.refuel()
        turtle.select(15)
        turtle.digUp()
  else
        print("Good Enough")
end --#end if statement

I assume, based upon indentation of your program, you wanted this entire block to be your function.

Additionally, if statments are usually phrased like this:

if <condition> then

elseif <condition> then

else

end

As opposed to

if
  <condition>
then

else

end

It probably doesn't make a difference in performance, but does make it difficult to read.

Ok I removed that end and changed the formating based on your suggestion, I tried the program and now it gets stuck in a loop on the chestfuel function.

--ItemSort
local function itemsort()
  local n = 1
  while n < 15 do
    turtle.select(n)
    local item = turtle.getItemDetail()
    if item then
      print(item.name)
      if item.name == "minecraft:sapling" then
        turtle.transferTo(16)
      else
        turtle.dropDown()
      end
      n = n + 1
    else
      n = n + 1
    end
  end
end

--Dig a Tree
local function tree()
  turtle.dig()
  turtle.forward()
  repeat
    turtle.digUp()
    turtle.up()
  until turtle.digUp() == false
  repeat
    turtle.down()
  until turtle.down() == false
  turtle.back()
  sleep(5)
  itemsort()
  turtle.select(16)
  turtle.place()
end

--Refuel from Enderchest
local function chestfuel()
  itemsort()
  print("Checking Fuel Level")
  if turtle.getFuelLevel() < 30 then
    print("Refueling")
    turtle.select(15)
    turtle.placeUp()
    turtle.suckUp()
    turtle.select(1)
    turtle.refuel()
    turtle.select(15)
    turtle.digUp()
  else
    print("Good Enough")
  end
end

--Main Script
while true do
  turtle.select(1)
  local success, front = turtle.inspect()
  if success then
    if front.name == "minecraft:log" then
      tree()
      end
    elseif front.name == "minecraft:sapling" then
      turtle.turnLeft()
    else
      turtle.turnLeft()
  end
  chestfuel()
end

Given that the chestfuel() function doesn't contain a loop, I highly doubt it's the culprit.

itemsort does have a loop, but it should be ending properly. I would restructure it as a numeric for loop.

Example:

for i = 1, 15 do
  print( i )
end

Your tree function has a small, probably unrelated, issue with it was well:

  repeat
    turtle.digUp() --#attempt to dig up
    turtle.up() --#attempt to go up
  until turtle.digUp() == false --#try to dig up again, but this time noticing whether or not you dug anything

  repeat
    turtle.down() --#attempt to go down
  until turtle.down() == false --#attempt to go down, but notice if the attempt was successful

It will work as intended, however unnecessary turtle calls are made.

I'd do something like this:

while turtle.digUp() do --#while we are digging something
  turtle.up() --#go up
end
while turtle.down() do end --#while we can go down, we go down.

These are minor issues though. I recommend adding print statements to where you think the problem area is, printing variables. This will help you understand what your code is doing wrong (or right).

Adding the print statements in helped, I got it working properly now, thank you for helping and for the tips.