Hi mcgee10,
Please try reseating the ink tanks and printhead in your PIXMA MG7520. To do this, please follow the steps in this article:
https://support.usa.canon.com/kb/index?page=content&id=ART141309
If the printhead error persists, your PIXMA MG7520 would require service. You are eligible for Canon's Upgrade Program. This is for out of warranty units which have been diagnosed to require service, or for some reason are incompatible with a new or upgraded system. This option allows you a one-time opportunity to purchase a replacement product, discounted from the list price.
If you would like to take part in this option, please call our Sales Department at (866) 443-8002 Monday through Saturday, 9am to 9pm. Let them know you have been working with technical support and the Canon Upgrade Program was offered.
