Garmin Express: Unable to add device. Unable to log in

Hello,

Today I updated to the latest version of Garmin Express and also wanted to install my new Garmin 840. However, whilst the device is found (takes a while), I am unable to click "Add device". Nothing happens, the cursor does not change and the screen does not change or acknowledge any activity. Eventually, the sign-in page pops up, asking for username and password. But I cannot type anything. I have unstalled and reinstalled Garmin Express already and the problem persists. Not sure where to go from here as I am unable to sync my new device to GE and even log into it. Any ideas?