So, I installed 2019.2 and after creating a new project, attempting to run the default empty scene, i get the following error:
“Copying assembly from ‘Temp/Assembly-CSharp-Editor.dll’ to ‘Library/ScriptAssemblies/Assembly-CSharp-Editor.dll’ failed”
Any ideas on how I can fix this? I also have 2017.2 1f1 and it works just fine.
I have seen this error crop up typically when you’re trying to create a build a second time… while the built application is still running from the first time. Are you sure that you didn’t have your built app running when you attempted a build?
I didn’t even attempt a build. I just tried to use the in-editor player and got this message.
Hello! This issue seems similar to another issue: https://issuetracker.unity3d.com/issues/errors-regarding-failing-to-open-temp-files-when-opening-a-project-in-a-separate-hard-drive
Sadly, our developers weren’t able to reproduce it. The cause of this issue seemed to be the usage of external hard drive, or Editor not having the permission to move the specified files. Please make sure that you are able to access the created project folder by normal means or try to run Unity as an administrator.
Well, it is similar, but I don’t think it’s related to using an external drive, at least that’s not my case. I have two internal drives and 2017.2.1f1 works just fine loading projects from either drive.
I did, however, uninstall 2019.2.1f1 and installed 2019.2.6f1 and, upon creating a new, blank 3D project, I get no errors. However, I can’t install or uninstall any package using the package manager without getting the exact same error. If i don’t mess with packages at all, I can work just fine… but I need packages… lol
Have you checked if the Editor has the permissions to modify files in these directories? Usually running Unity with Administrator mode is enough to test this. Also, could it be that the project path is super long (longer than ~230 symbols)?
Yes, permissions are all set correctly, nothing changed. I have run both, the Hub and the Editor in Administrator mode and the same thing happens.
I have uninstalled all other versions of Unity I had and tried again with 2019.2.6f1 to no avail. Blank project works fine. Both 3D blank and Template projects generate the errors if I do anything using the Project Manager UI. Even simply updating the Test Framework or the Rider Package, or even downloading a package I don’t have.
The screenshot shows the error JUST after I updated the Test Framework. I could play the scene with no errors before. I have to create a new project, because removing that package doesn’t solve the issue.
Google “unity copying assembly failed”. In particular, the “Answers” link may help.
Nope, those didn’t help. Also, the path to the project is not long at all. I’ll try refreshing Windows at some point this week 
Ok, so, at this point, I’ve tried pretty much everything. As long as I don’t touch the package manager, I can work and use Unity just fine. But even if I don’t, I never know if some 3rd party code or package will, and when it does, the same error pops up. The project is not workable on, anymore. I have to start from scratch. I’m at a loss here…
i am having issue similer to this but when i try to create a new project and it opens up it shows 1 to 3 errors all blank double clicking them does nothing when i try to play in-editor please help i have tried different versions of unity and it seems its only on windows as on linux it works just fine