Using Catalina beta 10.15 (19A558d) & iOS Beta 13.1 (17A5831c) Sidecar screen is black. If it turn on show sidebar, then I see only the sidebar. If I turn on Touch Bar, the screen adjusts, but I don't see anything different. Also, the System Preferences for Sidecar constantly blinks on its own every 2-3 seconds, like it's refreshing the Sidecar setting screen. Finally, with the last beta of both iOS and MacOS, the iPad screen stays connected. Previously it would disconnect every couple seconds but now has the behaviour I just described. I have iPad pro 12.9 3rd gen and MacBook Pro 2018. My host OS is Mojave 10.14.6.