I am running a code that uses arcpy.sa.ExtractByMask but it is saying the tool isn't licensed.

I know I have spatial analyst licensed and the tool works fine within arcmap itself. Anyone ever come across this?

Edit:

arcpy.CheckExtension('Spatial')

returns 'Available'

Edit:

When I run the extract by mask tool for 1 image in arcmap the snippet returned is:

arcpy.gp.ExtractByMask_sa("D:/Sheyenne/Atmospherically Corrected Landsat/Just_bands/LT50300281984137PAC00_sr_band3.tif", "D:/Sheyenne/sheyenne_area_poly.shp", "D:/Sheyenne/Atmospherically Corrected Landsat/Practice_band_clipLT50300281984137PAC00_sr_band3.tif")

I then try to run this in python:

import arcpy

arcpy.gp.ExtractByMask_sa("D:/Sheyenne/Atmospherically Corrected Landsat/Just_bands/LT50300281984137PAC00_sr_band3.tif", "D:/Sheyenne/sheyenne_area_poly.shp", "D:/Sheyenne/Atmospherically Corrected Landsat/Practice_band_clipLT50300281984137PAC00_sr_band3.tif")

and the error returned is:

ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000824: The tool is not licensed.
Failed to execute (ExtractByMask)