After upgrading DNN from 5.6.x to 7.1.1 (using recommended path), I cannot access the file manager.  I did install the repository, just in case that was the issue, but it did not fix anything.  Here is the error message I receive

Error: File Management is currently unavailable. DotNetNuke.Services.Exceptions.ModuleLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.Modules.DigitalAssets.Components.Controllers.DigitalAssetsController.GetFolderViewModel(IFolderInfo folder) at DotNetNuke.Modules.DigitalAssets.Components.Controllers.DigitalAssetsController.GetRootFolder() at DotNetNuke.Modules.DigitalAssets.View.get_RootFolderViewModel() at DotNetNuke.Modules.DigitalAssets.View.InitializeTreeViews() at DotNetNuke.Modules.DigitalAssets.View.OnLoad(EventArgs e) --- End of inner exception stack trace ---

 

Repository module is not related. you might perform a recursive sync in Admin file management and retry.
if this doesn't help, check /Portals/default for files and folders with special characters in the name or really big size.

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Cheers from Germany,
Sebastian Leupold

   

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I figured out our particular situation.  Somehow within the Folder Database Table the row for the Portal 0 was missing.  I created a new record row for the rootfolder specific to the Portal 0 and the File Manager is now appearing properly.