If you've tried to add a team to a course, but the search box didn't return any results, this article can shed some light on why that happened.
In order to add a team to a course, the team has to have at least one language in common with those that are available in the course.
To resolve this, add some or all of the course's languages to the team. After that, you should be able to add the team to the course with no further issues.
Note: For users to be able to do the course in all languages included in it, these languages have to be enabled for their team in the platform.