I updated the Studio on Friday (17th Feb) and then the firmware on my Demo 205 on Wednesday (22nd Feb). Then when I created a new project and tried to connect, the Testboard gateway connected but then couldn't find my device.
I closed the studio and then re-opened and tried again but it still didn't work.
I closed the project and
then studio and then reopened it (so it would open without any projects already on it) and tried to connect but it didn't work. I kept trying 4 or 5 more times and even waited 20-30 min for it to find my device.
I checked my FTDI drivers but they were the latest version so as a last resort I uninstalled and then reinstalled the same latest version of studio and then immediately connected my device before opening any projects. This worked and I have had no further problems with connecting so far.
I'm not sure what made it finally work.