Symptoms
When you share your PowerPoint timeline with other Office Timeline users and they open the slide, the Office Timeline ribbon is grayed out and they can't edit the visual using the add-in's controls. 
Overview
Typically, this situation occurs when the shared timeline slide is opened with an older version of Office Timeline than the one it was originally created with.
Solution
To solve this issue, please instruct the colleague you shared your timeline with to download and install the latest version of Office Timeline.
If the timeline slide isn't editable after updating Office Timeline, don't hesitate to contact us at support@officetimeline.com and we'll get to the bottom of the problem.