This is related to [Link Removed], and possibly the same issue. It is still not possible to open a generated.h file from within a project solution. I was able to reproduce this in both a binary Engine installation, as well as in an Engine built from source code. Two co-workers were only able to reproduce this in an Engine built from source code. Binary Engine installations worked correctly for them.
RESULT:
An error is displayed stating that the file cannot be found in the current directory or build system paths.
EXPECTED:
Visual Studio opens the generated.h file.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-67548 in the post.