Why are the Offerings Blank under Edit Assignment?

Summary:

Navigation: My Client Groups - Learning - Courses - Search for a Course (with available offerings already scheduled) - Learners - Filter 'Assignment Status' to 'No Offering Selected' - Highlight Learner - Click 'Edit Assignment' - Click 'Select' Offering

Content (required):

When following the above steps, the search doesn't return any offerings despite there being ones scheduled. Does anybody know why this is? Please see below screenshots.