Take a look at this page: https://blog.jetbrains.com/clion/2016/10/clion-and-ue4/
At the top there is this comment:
Upd This post is valid for UE4 v4.18 and less. v4.19 has an integration in UBT to generated CMake out of it directly, but not all the PRs have been accepted for now, so it’s currently broken. When the things work, we’ll update the post. Sorry for the inconvenience.
It’s not completely clear if this means that just some new feature is broken, or if CLion just isn’t compatible with 4.19 at the moment. Might be worth contacting JetBrains to see if their support can help.