I am having this same issue with a new Ultra+ ZS-406. Was working great on my computer talking to tinySA-app yesterday and earlier today. I set up TCPUART on my phone to try using the unit remote, and that worked quite well. It is after this when I could
no longer connect via USB directly.? Windows 10 machine
tried MULTIPLE USB cables - no USB or COM shows up in Device Manager
tried various USB ports - no USB or COM shows up in Device Manager
tried both "serial" and USB" as connection options from the config menu - no USB or COM shows up in Device Manager
cleared the TinySA config ("1234") - no USB or COM shows up in Device Manager
restart computer and try again - no USB or COM shows up in Device Manager
tried different Win10 machine
"unknown" device shows up in USB controllers section of Device Manager
performed uninstall device on computer, power SA off, power SA on? - no USB or COM shows up in Device Manager