I recently upgraded from Studio 2014 to 2019 and have both versions on my computer. A client sent me a package created using Studio 2014 and when I try to open the sdlxliff I get the message "an unexpected error occurred while activating the document view". I get past that by clicking ok but then get the message "Object reference not set to an instance of an object" and this message continues to come up in every segment I move to. I read somewhere that I should try deleting some files (basesettings, usersettings and plugincache) and restarting the program, but this has not helped. 

I have only had this problem since installing Studio 2019, which works without any problem. 

This is urgent so I would appreciate any help or ideas you could offer.

In case it's helpful, here is what I saved from the error message (Greek to me):

<SDLErrorDetails time="1/17/2019 3:03:01 PM"><ErrorMessage>Object reference not set to an instance of an object.</ErrorMessage><Exception><Type>System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type><HelpLink/><Source>Sdl.TranslationStudio.Editor</Source><HResult>-2147467261</HResult><StackTrace> at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocumentOutline..ctor(TranslatableDocument document)
at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.get_DocumentOutline()
at Sdl.TranslationStudio.Editor.TranslationEditor.SideBySideDocumentEditingView.GetActiveDocumentOutlineNode()
at Sdl.TranslationStudio.Editor.TranslationEditor.SideBySideDocumentEditingView.ManageActiveOutlineNodeChanged()
at Sdl.Desktop.Common.DelayedExecutable.Execute()
at Sdl.Desktop.Common.DelayedExecutionEngine.Timer_Tick(Object sender, EventArgs e)
at System.Windows.Forms.Timer.OnTick(EventArgs e)
at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)</StackTrace></Exception><Environment><ProductName>SDL Trados Studio</ProductName><ProductVersion>11.0.0.0</ProductVersion><EntryAssemblyFileVersion>11.2.4435.12</EntryAssemblyFileVersion><OperatingSystem>Microsoft Windows 7 Home Premium </OperatingSystem><ServicePack>Service Pack 1</ServicePack><OperatingSystemLanguage>1033</OperatingSystemLanguage><CodePage>1252</CodePage><LoggedOnUser>Tarani-HP\Tarani</LoggedOnUser><DotNetFrameWork>4.0.30319.42000</DotNetFrameWork><ComputerName>TARANI-HP</ComputerName><ConnectedToNetwork>True</ConnectedToNetwork><PhysicalMemory>16714988 MB</PhysicalMemory></Environment></SDLErrorDetails>

Thanks!