I've touched on this in https://intellij-support.jetbrains.com/hc/en-us/community/posts/360003403420-Jupyter-Community-Support-2019 but with more recent developments think a more general warning to other seems appropriate. The new 2019 Community Edition of PyCharm not only removes the existing support for Jupyter (moving it to the Pro license only) but seems to break Jupyter files that it opens! In my case I'm having to search for ways to repair a notebook now and/or manually transfer the code from the underlying json to a new notebook! I've lost a lot of work in this.
So for others using Jupyter in the CE of PyCharm, I'd HIGHLY recommend you think carefully about upgrading before you do so!