As online course pages are produces dynamically using parameters, Google will often skip the indexing of course pages when it is crawling the web site.
To instruct Google to include these pages you will need to use the Google Search Console
Once you are setup in Google Search Console with your site, go to the "Crawl" menu and then to the "URL Parameters" sub-menu.
Here you will see the parameters that Google has picked up. We need to change ID1, ID2 and ID3. For each one press the "Edit" on the right and change it's settings so that they look like the following.
Once this is done Google should start picking up every course page and indexing it on Google searches.