How do fix the error "could not be compiled. Try rebuilding from the source manually"

Hello everyone, IM doing an Unreal Engine 4 tutorial series and I’m instructed to open their game but whenever I open it, I get the error of “BullCowGame could not be compiled. Try rebuilding from the source manually.” What do I do to fix this? This was made with Unreal Engine 4.22 so that might be the problem but I don’t know.

Thank You,

Yours Sincerely, Olezka06.

I am having the same problem with a project that I want to upgrade from UE 5 preview2 to UE 5 release.

And I don’t know how to “Rebuild manually” the project to update it to the new version of UE 5.

Can anybody help me?
Greetings and thanks in advance


facing the same issue, if anyone knows about this, kindly help. thank you

So, What you wanna do is open the solution file (.sln) if it’s not there then first right click on your ProjectName.uproject and generate visual studio files.

Here my project name is GoogleTTS yours might be different

once the .sln appears open it using visual studio or Rider then press ctrl+shift+B in your case it will throw some errors and those are the cause of problem most likely.

Post the errors.


*Info for the people who don’t know how to rebuild (have never done it before):
You need Visual Studio Community (not Code). After its installation you will most likely run into the next error, which seems to be common with UE5:

A fatal error occurred. The required library hostfxr.dll could not be found.

If so, continue following this info to install the right version of .NET Core:

After that you should be able to rebuild just fine in VS.



I know this is over a year old (and probably breaks some rules about digging up old threads to comment on), but I’m surprised that the situation I’m about to describe is not mentioned here because it’s something that legitimately could happen. More specifically, it’s the fact that this only works if you had at least one C++ file in the project before the problem occurred; if this is not the case, you unfortunately can’t generate a solution for Visual Studio because there’s literally nothing to include in one.

If this happens, just create a new project. Name it whatever you want (this will be changed later), then go into your old project and copy over the contents folder to the new project. Note that simply copying the C++ files to the old project and generating solution files from that won’t work - Visual Studio will only complain of missing files which can be confirmed in the solution explorer, but this unfortunately is not fixable as far as I know. Once the contents folder has been copied to the new project, delete the old one and rename the new project to whatever the old project was called. You can then open the new project, and everything should be good to go again.

If I understand your post correctly, this error would occur from a trigger you don’t mention (an introduction of an unbuilt plugin perhaps?). What is the cause? You could always build a plugin from within another project. I keep some core plugins I reuse in a c++ project and symlink them to other projects.

File names? Anything missing I think you should make yourself (.cpp, .h, .cs).