I am very glad and relieved to announce: OnVUE finally worked, and I finally passed 1z0-809 exam. I just passed: 71%, not hall-of-fame-material, but fine for me.
Has anyone had similar issues with the PearsonVUE online exams? I tried the exam two or three times before, and the software just did not work on macOS. I tried on at least three individual Macs and got a bouquet of different error messages. I always said yes to all system requests, turned off all firewall etc, still did not work. The exam had to be reschuled each time. If someone has the solution - I would be glad to read it. OnVUE worked just well about one year ago on my Mac for my OCA 1z0-808 exam.
Today, I had a Windows machine my sister-in-law gave me. Did not work perfectly, I once had to re-connect when OnVUE suddenly quit. But it worked fine after that.
As promised, I’d like to provide how I prepared. I have read Christian Ullenboom’s German Java books (“Insel”) and Michael Inden’n book on Java 8 new features, OCP study guides by Kathy Sierra and Bert Bates as well as by Scott Selikoff and Jeanne Boyarsky. I attended some video courses at udemy.com: by Christian Ullenboom, by Tim Buchalka. To practice, I had the OCA/OCP8 practice book by Scott Selikoff and Jeanne Boyarsky and a mock test again at udemy.com.