Sidecar via USB doesn't work to use iPad Pro as second display for iMac

I'm using my iPod Pro as a second display for my iMac. After updating to macOS Sequoia (iMac) and iOS 18.0 (iPad) I'm getting an error message when I try to connect via USB cable (connecting via WiFi works): "Unable to Connect to iPad Pro. A miscellanious error occurred (-6745)" and the iPad Pro immediately locks its screen. As it has worked with macOS Sonoma, I wonder what to do. I tried every trick I could found, but to no avail.