Attempt to index ? (a nil value)

ive got a clock program that was running yesterday, but now doesnt want to cooperate.
my program is called "startup"

function infiniteLoop()
while true do

m = peripheral.wrap("left")
m.setTextScale(3)
local time = os.time()
time = textutils.formatTime (time, false)
mon.clear()
mon.setCursorPos(1,1)
mon.write(time)
sleep(1)
end
end
infiniteLoop()



and the error message that it gives me is "startup:8: attempt to index ? (a nil value)"

any ideas that could help would be greatly appreciated.

You're wrapping the peripheral as "m" but you try to use it later as "mon".

Just change your first two monitor-related lines to "mon" instead of "m".

mon = peripheral.wrap("left")
mon.setTextScale(3)