Unfortunately, we’ve recently discovered OmniPlan (and OmniOutliner) compatibility issues with macOS 10.14.4. If you haven’t already updated your Mac to this release of Mojave, we recommend waiting for the next macOS update.
Ken shared a bit more detail about this on our blog:
Good afternoon, readers! It’s incredibly rare for us to have to do this, but I need to let our Mac customers know that the 10.14.4 version of Mojave which shipped a few weeks ago (on March 25, 2019) has a drawing bug which makes windows with large CoreAnimation layers fail to draw. In particular, OmniOutliner and OmniPlan customers have been telling us that since upgrading to 10.14.4, they will open some documents and end up seeing… nothing. Perhaps some empty borders around the window. (Or if another window is dragged over the space where that window should be drawing, they’ll see a trail of its old pixels.) This is most likely to affect customers who are using older hardware, but it also affects large documents on newer hardware.
We’re working with Apple to get this resolved as soon as possible, but for now it appears there’s nothing we can do to resolve this on our own. We’ll provide an update as soon as a fix is available. In the meantime, I’m afraid we need to recommend that any OmniOutliner or OmniPlan customers with older hardware or large documents hold off on updating to 10.14.4. (Earlier versions of Mojave are fine.)
If you have already updated your Mac to macOS 10.14.4, and need help accessing a project that opens in this state, please send our Support team an email! We’ve come up with a couple workarounds that might help get you up and running until Apple can address this issue. Our Support team can be reached by email at firstname.lastname@example.org