When I try to create a new event the dialog comes up. I enter title and general notes. Press OK and the following message appears "Select a valid collection first" Korganizer version is 5.5.3 on Kubuntu 17.10 I have been using Korganizer for about 1 month; this problem has just emerged. Nor can I edit previous events. I can return to using Google calendar so this is just annoying. I also use Thunderbird and have used its google calendar add-ons and they worked perfectly. I do prefer Korganizer. The other thing I noticed is with May 2018 and earlier not all event entries are shown in Korganizer yet they exist. With Thunderbird you need to install calendar add-on then an extra add-on called Provider. It allows bidirectional editing with Google calendar. Know idea if this helps Best wishes Andrew
The problem fixed with the latest version of korganizer 5.15.1