Thank you. Lets try these repairs in order.
First, turn your Canon printer off. Then..
Choose System Preferences from the Apple menu.
Click Printers & Scanners.
In some versions of OS X, this preference is named Print & Scan or Print & Fax.
Control-click anywhere in the list of devices on the left, then choose “Reset printing system” from the shortcut menu that appears.
Once the printing system has been reset, run this repair next
Open your finder ( magnifying glass ) type in disk utility, and launch the disk utility application.
On the left side of the disk utility window, click your mac hd, then at the lower right hand side, click repair permissions .
Once it says permissions repair complete.. All we need to do now is download a fresh copy of the printer software, install it, and this will install the printer and get it working again.
To get the driver, go to this page https://www.usa.canon.com/internet/portal/us/home/support/details/printers/inkjet-multifunction/mg-series-inkjet/pixma-mg3620?tab=drivers#Z7_MQH8HIC0L88RB0AMD0F1Q42K25
And under recommended downloads download the "MG3600 series Full Driver & Software Package (OS X) 12/10/ 158.06 MB"
Once you download and install that file, it will reinstall your printer and you should be good to go!
If you get stuck or run into any issues, let me know. And if you would prefer I can connect to your mac from here and run through the repairs and the printer install process on screen for you, in person. Let me know if youd like to try that option.
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Senior Technician and Network Switching Systems Operator / Maintainer.