Step 1: Click Preferences
Step 2: Click Calendar Sharing *(if you do not see this option, check with your Enterprise Manager or Adminstrator to have access enabled)
Step 3: Verify that the email address or username with whom you are trying to share is typed correctly
Step 4: Verify that the other person has enabled viewing of your calendar from their account (use the checkbox next to the calendar name to display)
Step 5: Verify that the person has your calendar set to a color that can be viewed