Hi zoe001fa,

Please follow these steps:

 1.  Press the Windows key on your keyboard and the letter R, then let both go.

 2.  In the Run window, please type CONTROL PANEL and click OK.

 3.  Click on View devices and printers (or Devices and printers, depending on the view).

 4.  Double click the Canon MG7100 series printer.

 5.  In the window that appears, if there are print jobs listed, please click on Printer and then Cancel All Documents.

 6.  Once gone, please close that window.

 7.  Right click the Canon MG7100 series printer and left click on Remove device.  If there are more than one listed, please remove all until all Canon MG7100's are removed.

 8.  Click on Control Panel in the upper left corner (or the Back button).

 9.  Click on Uninstall a program (or Programs and features, depending on the view).

10.  In this list, please click on "Canon MG7100 series MP Drivers" and then click Uninstall at the top.

11.  Follow the on screen prompts to uninstall the drivers.

12.  Once gone, please reboot the computer.

When the computer restarts, we will reinstall the drivers:

 1.  Please use the following link to access the downloads for your PIXMA MG7120:

https://www.usa.canon.com/internet/portal/us/home/support/details/printers/inkjet-multifunction/mg-s...

 2.  Click the Select button next to "MG7100 series MP Drivers Ver. 1.01".

 3.  Click the Download button.

 4.  Once the download is complete, please open your downloads folder.  You can open the downloads folder by pressing CRTL and J while in the web browser.

 5.  Double click "mp68-win-mg7100-1_01-ejs.exe" to begin the installation.

 6.  Follow the steps to reinstall the drivers.

Once reinstalled, please attempt to print.