The "Synchronize" button on the [[Invantive Control for Excel/User Interface/Control Ribbon|Control ribbon]] is enabled only when synchronising can actually do something. It stays greyed out in the following situations, which are checked in this order. - No workbook is open, or the open workbook holds no [[Invantive Control for Excel/Repository/Repository|repository]]. A workbook which was never made into an Invantive Control workbook has no model to synchronise. - The workbook holds a repository but no [[Invantive Control for Excel/Concepts/Model|model]]. - Design mode is switched on. A model is being edited then, so uploading and downloading are withheld until design mode is switched off again with the same toggle button on the [[Invantive Control for Excel/User Interface/Modeler Ribbon|Modeler ribbon]]. - The model holds no [[Invantive Control for Excel/Concepts/Block|blocks]]. There is nothing to fill or to write back. - The logged-on user is not authorised to synchronise. The licence and the permissions of the user decide which ribbon buttons are available at all. The split part of the button follows separately: "Download Only", "Upload Only", "Publish to New Model" and "Remove Downloaded Facts" each appear only when the user is authorised for that specific action. When none of them is available and synchronising itself is not either, the whole split button is disabled. Restarting Microsoft Excel does not change any of this, since none of the conditions depends on the state of Excel itself.