Ensure that you do not have any HTML coded into the Login area of Website Features.  Using HTML to add additional links or font styles can cause these buttons to no longer function.
  1. Navigate to Communities > Special Events > Friends Asking Friends > Kintera Thon
  2. Hover over your event and click Website Info
  3. Click Website Features
  4. Scroll down to the "Login" section
  5. Ensure only text appears in the social sharing default text, and remove any HTML
  6. Click Save
  7. Navigate back to the Webinfo Checklist and click the green Publish This Event Now button

If this does not resolve your issue Chat With Support and reference this article.