The error Incomplete Visualization may appear when, for example, selecting the same dimension twice on a chart. Additional root causes for Incomplete Visualization when fields are missing or the app is not loading completely can be found in Warning Message "Incomplete Visualization" Shown In Qlik Sense Visualization.
For instances in which the warning is caused by incorrect selections and the app not reverting to a correct state, follow these instructions:
Create a bookmark with the correct state of the app. Save layout needs to be selected when creating the bookmark.
Right-click the bookmark and publish it to all users.
Republish the app to the space or stream.
Ask the user to apply the bookmark to reset the chart to the correct state.