You may need to look in Canvas and click on the Courses tab, then “All Courses” at the bottom of the list to see the unfavorited courses. Courses may be favorited by clicking on the star next to them in the list, but only 12 courses will show up in the Dashboard in any case.
Sometimes Canvas has delays in sending out messages so an alternative approach is to login to https://myosu.oregonstate.edu/, go to the Faculty/Advisor tab, and under "My Classes" you'll be able to email your students.
Where do I get help?
When you are signed into Canvas, click on Help in the upper-right corner of the screen. Choose the online chat or phone number to contact a support person 24/7. They’re really good at what they do!
and here are more detailed descriptions with examples from Dartmouth.
What should my students know about Canvas?
5 Things for OSU Students to Know about Canvas – take a look at this general guide for students; you may want to include a link in your course site, or in your communications with students at the start of the term.
This is great, but I just want to jump in. Are there some videos I can watch to get going?