Getting Error defining FVector2DHalf - Unrecognized type 'FVector2DHalf' - type must be a UCLASS, USTRUCT or UENUM

Hey,
I can’t define a FVector2DHalf without getting a “Unrecognized type ‘FVector2DHalf’ - type must be a UCLASS, USTRUCT or UENUM” Error.
I’ve included the Headerfile and Intellisense suggests it and finds the definition in the files but I can’t compile. I already red all of the connected threads with this error but nothing helped. What is going wrong here?