To access the link of the Garmin page for the download, click the right mouse button and choose "show source code" and you can download the file FirmwareUpdateforGTMxxTrafficReceiver_550.rgn, which must be compatible with the GTM20 (not being, is not installed). To install it, the easiest way is to drag the file onto the icon WebUpdater with the GPS connected to your computer. When GTMxx gps is turned on it will be updated since that the installed firmware version is lower, otherwise nothing will happen. With the GTM connected, check in Tools, Setup, About, the version of software installed.