I’m having the same issue. Never experienced this prior to 5.6. Incredibly frustrating, surprised no one else raised this problem sooner.
Issue seems to affect all imported assets that are not actively loaded.
For example, if I create a folder under Content called ‘Meshes’ and import an .fbx file, then close and re-open Unreal Editor, I can no longer see the Meshes folder in the Content Browser. If I manually browse to that location with Windows Explorer I can still see the Meshes folder in MyProject\Content\Meshes and the .uasset file in it. No folders or assets have been deleted, the Content Browser is just failing to show it for whatever reason.
Workaround: Drag and drop the fbx somewhere into the current default map so it loads at launch.
Additional:
If I click on the Gear icon on the right hand side of Content Browser, ‘All Folder’ is already ticked.
If I right-click on the Content folder and select ‘Validate Assets in Folder’ I see no error messages and the issue persists.
If I right-click on the Content folder and select ‘Update Redirector Referrences’ I see no error messages and the issue persists.
I’ve also been having this issue. It’s incredibly frustrating. The only way I can keep assets visible in the Content Browser is having them loaded somehow in the default map.
Update: Launching the project through Epic Games Launcher instead of building it from the IDE fixed it for me. It seems there were some missing binaries causing the issue.
Edit: After the issue cropped up again, I just ended up migrating the files to a fresh project. I’m still unsure what exactly caused this.
I just moved to 5.6.1 and I am now getting this specifically in the content folder of my plugins. Static mesh, skeletal mesh and animation assets all seem to be fine, but materials and niagara systems are very sporadic and only show sometimes when actively loaded.
I’d also like to add that I have been encountering this issue after moving up from 5.4 to 5.6.1
It seems to affect both manually created folders and subfolders and also content added through fab or through epic games launcher with the “add to project” functionality. It’s also not consistent meaning sometimes everything works just fine.
Perhaps worth mentioning that this happens in a project without any source control enabled so it can’t be attributed to source control shenanigans.
I did solve it by deleting binaries, intermediate and saved folders but I assume it’s a matter of time before this problem returns.