Having trouble with a basic clock program

Wrote a clock program for my terminal glasses and it was working fine. server Im on restarts and when i log back on suddenly its broken

error message:

clock:15 attempt to index ? (a nil value)


CODE:

glass = peripheral.wrap("left")
function addBox()
  glass.addBox(1,20,80,10,0xFFFFFF,0.2)
end

function drawTime()
  time = textutils.formatTime(os.time(), false)
  glass.addText(5,21,"TIME: " .. time, 0xFF0000)
  end

function start()
  while true do
  glass.clear()
  addBox()
  drawTime()
  glass.sync()
  sleep(0,1)
  end
end

start()

Assuming line 15 reads "glass.clear()", that indicates that peripheral.wrap("left") returned nil, which means the computer did not detect a peripheral to its left.

If the glasses bridge is still sitting there, trying breaking and replacing it.

THis worked, thanks! it seems i need to do this everytime i log off and on though, very wierd.