In my experience with USBridge, not DigiOne, after clicking on the Reboot button in the WebGUI, the GUI is left in the ‘cycling circle semi-transparent overlay’, as you so well described. The fix is to physically unplug USBridge (disconnect from AC), count to 10 and plug it in again. I’m not sure whether this might cause eMMC card corruption, or not, but is the only way for the USBridge to come back online. I’m currently waiting for @rahulkc_s to respond on this issue in a private troubleshooting thread for this issue.