Thank you! Exactly the same scenario when creating a plugin and changing to PreDefault worked for me.
Still happens in UE5.2. Created a c++ class derived from Character. Compiled successfully. Created a blueprint from this class. Compiled successfully. Closed UE. Opened it again. Error âBlueprint could not be loadedâŚâ.
I solved by disabling Live Code, rebuilding, closing the editor and opening it again. Live Code is a source of many problems and I think that it should be disabled by default.
ERROR:
Blueprint could not be loaded because it derives from an invalid class. Check to make sure the parent class for this blueprint hasnât been removed! Do you want to continue (it can crash the editor)?
VERSION: Still happens in 5.2.1. (even when using plugins like ImGui)
SOLUTION: Deleted âBinariesâ folder (as mentioned by @AleAB94 and @sandolkakos) and its working so far. I donât know if this is releevant or not, but after deleting âBinariesâ, I right click on the .uproject file and then âGenerate Visual Studio Project Filesâ (as an added step), then double click on the .uproject file, and it started working.
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This is the way.
1 Like
This worked for me. Thanks
Same Issue. Im using UE 5.2.1 and disabling live coding and restart Engine and then manuelly complie works for me. Thanks
This was the solution to my issue. There was broken redirect in projectroot/config/DefaultEngine.ini
For anyone struggling with this open up the DefaultEngine.ini file and look at the list of redirects.
It will have the header [CoreRedirects] and a list of items like
+ClassRedirects=(OldName=ââ, NewName=ââ)
+PropertyRedirects=(OldName=ââ, NewName=ââ)
+StructRedirects=(OldName=ââ, NewName=ââ)
Ctrl+F in that file and make sure you have no loose ends for the broken blueprint class in question.
It can be setting your class to an invalid class here so just make sure.
Hope this helps someone 
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I found this thread due to also encountering this issue in UE5.3.0.
Create a new blueprint from a class I created, or change the parent class of an existing blueprint. Save everything, close everything down and come back to this.
I also noticed that the C++ classes folder would not show up until I started Visual Studio from the Unreal Editor.
Curiously to me, a ton of classes were not listed when trying to set a new parent (from non). Choosing one of the still possible parents, then trying to undo results in a fatal error.
Solution #1: is to delete the binaries folder in your project.
Solution #2: is to open only your Visual Studio solution and build your project.
Hopefully someone discovers these solutions and it helps them too
Are you programming with the editor open?
Close UE, build the c++ code, create core redirectors if necessary, restart the editor, check every BP one by one and save them if they updated properly. After saving all BPs remove the core redirectors.
Thanks for checking.
The issue seems to be with the live coding feature?
Once I did those solutions I shared I donât have the issue at all anymore, even with the editor open.
This is one possibility yes. That is known for issues.
It might be the reason in some other cases but iâve had the exact same issue without ever renaming the class, all i did was create a child class and make my player character a child of that second class, no renaming involved.
Same problem in 5.3, deleting Binaries fixed it
This will help you to reparent a Class in case if you renamed the class and some BPs crash an Editor.
canât belive it, but it is still an issue in 5.4⌠deleting Binaries folder will fix it
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This Method Work For Me
This decision helped me. We select blueprint â asset actions â reload
Hi, New to Unreal, not new to Game Dev or programming. My question. How can a problem as this exists aafter that many years and that many versions? Is this not fixing problem year after year often the case in Unreal? Asking because then I wonât be investing more of my time in Unreal and go back to what i allready know.