What can I do to resolve this error and get back to sync’ing my calendar on my Android?
A quick solution should be to delete the whole recurring event (not only an instance) on your Android device, which should DELETE it from your server, too.
Which server software do you use?
I didn’t want to do what you suggested, but as I thought it through, your recommendation makes sense. On my Android I went back to the date of the original appointment (24 Aug 2016), and deleted all recurring instances of the appointment. Now all the instances of the appointment are indeed deleted, both on the Android and on the server-side. And my Android doesn’t throw an error anymore. I can sync my calendar successfully again.
My company uses MicroFocus (Novell) GroupWise.
Thanks so much for your guidance.