Problem that the project cannot be saved in UE4

Table of Contents of Series Articles

Preface

Cancel: Stop saving all assets and return to the editor.
Retry: Try saving the asset again.
Continue: Just skip saving the asset.

When I clicked Continue, closed the project, and then reopened the project, I found that all the previous content was lost.

1. Solution

Cause of the problem: The same project was opened twice.
Solution: Open only one project and then save it normally.