Randy75
Do you happen to have the Model numbers of the RokuTV. (look on back on TV).
I tried a factory reset with USB a few days ago and also received the "invalid" file error so not too sure if this method is still viable after the 11.5 OS update. (or if Roku just needs to update the existing update.roku files on their end).
You can try factory resetting again and selecting "No connection", just like you did the first time when using the USB method. Then perform a System Restart on the RokuTV. (Settings/System/System Restart). When it reboots, you can try connecting to a mobile hotspot (if available to you), and try to update the RokuTV in that manner.