secondary google calendars not syncing

Hello!

I have been successfully syncing my gmail account (mail, contacts, and calendar) with my iphone for several years now.  Recently, my secondary calendars have stopped being able to be accessed through the native calendar app. I don't know why. 

I've gone here: https://www.google.com/calendar/iphoneselect?pli=1 and checked all of my calendars, but still only the main one syncs.  My company uses google calendar to keep track of my comings and goings, and they're going to make me switch to Android if I don't get this sorted out SOON!

Thanks for any help!