User is trying to check or un-check the Billable flag for time entries, but it does not seem to work. Clicking on the Billable flag does not change its state.
This happens when your security permissions restrict you from changing the billable status of entries. The security option that controls this in your Security Profile is Allow change billable/non-billable under the Time Entry module. You should ask your Core administrator to check this option in your profile if you want the ability to change the billable status. Check Core Help Center for details on customizing security permissions.