Can't print with .am1x file on Canon PRO-300

[mrswitters]

I have a Canon PRO-300. I would like to use an .am1x file to make a print with Canson Fiber Platine Rag paper. I've downloaded the .a1mx file and installed it using the Media Configuration Tool. It appears when I click on "Custom" in the sidebar of the MCT, so it does seem that it is installed correctly:

However, I do not see this as an option listed in the Paper Settings menu on the PRO-300 itself. (Note: I'm following the instructions on this page of Red River's website. Although the paper I'm using isn't a Red River paper, these were the clearest instructions for using an .a1mx file I could find.)

When I tap on Paper Type, I do not see "Custom" as an option, and thus I cannot choose the Canson Fiber Platine file I sent to the printer. (On the Red River tutorial page, "Custom" appears below "Card Stock." On my PRO-300, Card Stock is the last menu option; if I use the down arrow to go below that, it resets to the top of the menu.)

What am I doing wrong? 

[mrswitters]

Also, there is no "Custom" option in the "Media Type" dialog within the Mac printer driver when I attempt to print. This makes me think the .a1mx file isn't correctly installed on the PRO-300. But if it isn't, why does it appear in the "Custom" menu in the Media Configuration Tool? 

[EduardoAlemao · Accepted solution]

Go to System Settings > Printers > [your Printer] > Options and Supplies > Utility > Open Printer Utility > Media Information > Update the media information of the printer driver.

So long! This should update your printer with the new paper 😄 

[mrswitters]

Thanks, that solved the problem!