The link provided for validating the files i.e. http://validator.imsglobal.org/accessibility/ is not working. Its throwing an error of "Server Not Found" while accessing. Kindly provide a way to test the coomon cartridge files.
We do maintain a validator to test cartridges for IMS members, but no longer maintain the validator you reference above. If you are interested in validating and certifying Common Cartridges, there are several low-cost options for membership. You can see more details here: https://www.imsglobal.org/imsmembership.html