Hi Jacques,

The first thing to check is if Audience-based visibility is enabled - if so then only some courses may appear to some learners. You can check under Site Administration cog > Advanced features > and see if "Enable audience-based visibility" is enabled. If so, then the courses that aren't appearing likely haven't been made visible to any audiences. You can check that by going to the Course administration > Edit settings option and under the Audience-based visibility section see what the Visibility is set to. 

Thanks!

Wes