You might get the following error message when you:
- try to launch GoodNotes 4.
- launch GoodNotes 5 and tap "Import Data from GoodNotes 4" from the GoodNotes menu.
This error might occur if your GoodNotes 4 app wasn't updated to the latest version (GoodNotes 4.13.5), which is causing this incompatibility issue with the latest iPadOS version. Unfortunately, we have stopped supporting GoodNotes 4 since GoodNotes 5 came out.
As an immediate workaround, please offload GoodNotes 4 by going to iPad Settings > General > iPad Storage > GoodNotes 4 > Offload App. This shouldn't affect your data. Next, redownload GoodNotes 4. As GoodNotes 4 is removed from sale, you won't find it on the App Store, but you can redownload it from your Purchase History if you log in with the same Apple ID you used for the original GoodNotes 4 purchase. Then, you should be able to start the app.
Once you can launch GoodNotes 4, please consider getting GoodNotes 5 (if you don't already have it) and then migrate your GoodNotes 4 documents to GoodNotes 5 as soon as possible to keep your notes safe:
In case you're still hesitant to switch to GoodNotes 5, can you let us know why through this quick survey?
See also: I can no longer launch GoodNotes 4