This can be caused by setting the company as a "Sponsoring Company Only".  To change this setting:
  1. Select Manage for the TeamRaiser event.
  2. Select the Local Companies tab.
  3. Find the particular company that is missing and select "Define Sponsorship Details".
  4. Uncheck Sponsoring Company Only.
  5. Save.
Now the company should be included in the top 10 list.  If this setting did not resolve your issue then please contact support and reference this kb article.