I update my unity from 2018.3.12 to 2019 1.4,and open my 2D project with new unity. It says that my project need to be upgrade. But when the progress finished,it opened a 3D project and my assets and my scenes were all cleared. Even if I open the explorer, the files in the assets folder were all missing but an image. The image was the last one I imported in before I update. The size of the project folder now is 52mb. I try to reopen my project with 2018.3.12 version, But it says that: An error occurred while resolving packages: Project has invalid dependencies: com.unity.package-manager-ui: Package [firstname.lastname@example.org] cannot be found Package email@example.com has invalid dependencies: com.unity.ugui: Package [firstname.lastname@example.org] cannot be found Package email@example.com has invalid dependencies: com.unity.ugui: Package [firstname.lastname@example.org] cannot be found A re-import of the project may be required to fix the issue or a manual modification of /[my project path]/Packages/manifest.json file. Click on Retry to relaunch Unity and reopen your project. Click on Continue to launch Unity. Some or all packages may not be imported which may cause compilation errors I retried several times but all the same error. And I click on continue, it opened a 3D default project with nothing just like I opened in 2019 version. Can someone help me? I'm really worry about my project.