Putty, Byobu, Tmux and function keys

I'm currently trying to use byobu from PuTTY via ssh. I have currently putty-256color as Terminal-type string because otherwise not even Byobu bindings worked and I couldn't create new windows or move between them. I have Tmux backend and byobu-crtl-a set to emacs however I can't seem to make F keys work in either Midnight Commander or htop. I tried as suggested the Ctrl+a and Shift+F12 to enable them but I receive no message and still can't make them work.

What am I doing wrong? Thanks for the help.

Solution 1:

After reading it here I changed the session so that "Terminal → Keyboard" has the option "Xterm R6" selected.