If your Dynamics CRM Online instance has been upgraded to Orion (CRM2013) you will need to upgrade to the latest version of the Ribbon Workbench for CRM2013. Since the Ribbon Xml Schema has changed slightly with CRM2013, the old version will no longer work.

Upgrade Steps:

  1. Open Settings->Solutions.
  2. Locate the Ribbon Workbench solution and click 'Delete'
  3. Download and Import the Ribbon Workbench for CRM2013.
  4. Refresh your browser and navigate to Settings->Solutions where you will find the new Command Bar button:

Further reading:

  1. Ribbon 'XML' Workbench for Dynamics CRM 2013 with a silent 'XML'!
  2. 4 things you need to know about the Command Bar
  3. Restore a Button that has been removed from the CRM 2013 Command Bar