It seems you are experiencing issues with the Spine Plugin in various versions of Unreal Engine 5, even in a blank C++ project. Based on the information from the context, there are a few potential areas to investigate:

1. Asset Naming Conflicts: Ensure that your skeleton and atlas files do not share the same name up until the extension, as this can cause issues in UE 5.3 and possibly other versions. For example, skeleton.skel and skeleton.atlas will not work, but skeleton-foo.skel and skeleton.atlas will.

2. Build.cs File: Check that the SpinePlugin is correctly referenced in your project's Build.cs file. This is a common requirement for integrating the plugin into your project.

3. Visual Studio Compatibility: Ensure that your version of Visual Studio is compatible with the version of Unreal Engine you are using. There have been reports of compatibility issues affecting the build process.

4. Plugin Installation: Follow the standard procedure for installing the Spine plugin, which involves copying the plugin sources to your UE project and generating the Visual Studio project files.

5. Known Issues: There are known issues with UE 5.3 related to asset imports and other core engine problems that have been reported to Epic Games. These issues might affect your project if you are using this version.

If these steps do not resolve your issue, consider providing more detailed information about the specific errors you are encountering, as this can help in diagnosing the problem further.

Beeftor Thank you for creating a new thread!

You mentioned that you followed the steps in our “Getting started with spine-ue4” video, but could you tell us which part of the video caused the error shown in the screenshot you posted?
At about 1:35 in the video, it says that the following dialog box should appear, but have you gotten this far?:

Beeftor So, if you reopen the UE project where SpinePlugin has been installed, you will be able to see the error log? Or does the error occur when you create a new C++ project that has nothing to do with the project where SpinePlugin is installed?
Based on my testing using UE 5.5.3, I created a blank C++ project, closed it, installed spine-ue, closed the project again, and reopened it without encountering any issues. I then created a new blank C++ project, and that also worked without any problems. I would like to know exactly at which step the error occurs.

Beeftor Thank you for clarifying! I have confirmed that the error is indeed being output to the Output Log, so I have created the following issue ticket to fix it:
EsotericSoftware/spine-runtimes2821
(Based on my testing, even with this error log output, spine skeletons can be instantiated and animation playback seems to work normally).
We appreciate your patience while we work to resolve this issue.

Beeftor Hmm, that's weird. When I tried instantiating skeletons and playing animations, the skeleton data I used was also exported as a binary .skel file, but I didn't get that error. Could you make sure that the Atlas file and Skeleton Data file have different names? (This requirement is mandatory in UE 5.3 and later. For more details, please refer to the following section in the documentation: https://esotericsoftware.com/spine-ue#Updating-to-Unreal-Engine-5.3-)

If you have confirmed that the file names are correct and the import error still occurs, please send us a file that reproduces the problem via email: contact@esotericsoftware.com
Please include the URL of this forum thread in the email so we know the context. Then we can take a look at what's wrong.

Beeftor Sorry for the delay in testing. I installed UE 5.2.1 and tried it, but I still couldn't reproduce the problem. I was able to import the .skel file normally, and the Spine skeleton animation played normally in UMG UI. Could you send us your skeleton data file that reproduces the problem via email?: contact@esotericsoftware.com