It appears there is a bug with the new version of Teamviewer. It doesn't fully register or force full-screen mode when clicked. On the Desktop version, I had to minimize the top bar and hit the full-screen button twice for it to register to send keys. (I was already full screen). On the web app which I use quite frequently and need to be able to send keys for alt-tab and Windows key there does not seem to be an option.
I am quite unhappy with the new change and have no option to go back. The UI is fine, the problem is the program no longer does what it did 2 weeks ago. It also seems more unstable when it comes to connections, where it randomly disconnects. I hope that someone is working to fix these bugs, and wish it would have been tested before a mass deployment.
Again I need the send-keys option and the fact I can work from the browser makes it easy when I need to get work done, so please can someone fix this huge bug.