Recently I worked on one of the issues where Project Save was getting cancelled in the queue with error “Root element is missing”. Normally I always try “Save for Sharing” method to resolve this kind of issue. However Save for Sharing didn’t help to resolve it this time. The Save operation was getting cancelled at 0% in the queue with this error. That means the information from Project Client was not reaching to the Server. That made me think that issue is related to Project Local cache. After deleting project cache, the Save for Sharing worked on this plan and we were able to save the plan successfully.