Unable to add learner onto course

Summary:

Unable to add learner onto course

Content (please ensure you mask any confidential information):

When adding a learner onto any course you can find and select it in the search results but then it disappears upon selection. Other learners can be added fine. The person is an active employee with active user account and there are no user groups or access restrictions on the course ?

Version (include the version you are using, if applicable):

26B

Code Snippet (add any code snippets that support your topic, if applicable):