UEFN Wouldn't Open After V36.00 6/7/2025 Update

Development Getting Started & Setup
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UEFN wouldn’t open after the Fortnite V36.00 update today (Jun-7-2025). I’m running Win 11. I’ve had it installed and have been developing with UEFN for months. After the update, nothing happened when I tried to open it from the Epic Games Launcher. It seems like it tried to start, but then didn’t. And didn’t give any error.

I found the UnrealEditorFortnite-Win64-Shipping.exe executable and tried running it directly, as an administrator, from the C:\Program Files\Epic Games\Fortnite\FortniteGame\Binaries\Win64 folder. This generated the following error:

The code execution cannot proceed because tbb12.dll was not found. Reinstalling the program may fix this problem.

I hunted down the distribution of this DLL here:

And copied the correcttbb12.dll from it into the FortniteGame\Binaries\Win64 folder.

Now it works.

I’m not sure why that DLL was suddenly missing today, but I would have to assume the UEFN installer did something wrong??

Just thought I would point this out in case anyone else has the same issue.

UPDATE: Try the “Verify Files” command in Epic Games Launcher (as described below) to see if it resolves the issue before manually resorting to adding the DLL yourself.

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TYSM!! IT WORKS

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Thank you so much, now it works

4

got same problem, after verify the program it works

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I was able to get UEFN to launch by verifying files. I first clicked “Manage”.

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Then select the option to “Verify Files” by clicking Verify.

I can confirm it would not launch after Uninstalling and Reinstalling, but this did the trick. :wink:

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Hi!
This is how I solved it on Win 11:

I copied the tb12.dll from this folder:
C:\Program Files\Epic Games\Fortnite\Engine\Binaries
(not sure if this only exists when the epic games launcher is running)

And pasted it into the folder mentioned by lantram:
C:\Program Files\Epic Games\Fortnite\FortniteGame\Binaries\Win64

Then I started the epic games launcher and then uefn and everything seems to work again.

1 Like
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UEFN wasn’t launching for me either after the new season update.
What worked for me was going to Manage > Verify for both Fortnite and UEFN in the Epic Games Launcher. After verifying the files, it launched normally
Might be worth trying that first if others run into the same issue.

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