melly - yes, that is the menu button. Can you try touching farther to the edge? Can you try touching it repetitively? Can you try pressing a little harder? Have you had any other issues with the touch screen in that area with other apps?
CyberKnights is too old to properly detect which side of the tablet is pointing up. So it just picks a side and says that this is the up side. Some of us would like the other choice, for instance because we want to play while the tablet is charging, and the electrical socket is on the 'wrong' side of the bed/couch/desk etc. I am using this program. play.google.com/store/apps/details?id=com.googlecode.eyesfree.setorientation&hl=en
It is free and works fine with my marshmallow tablet, the nvidia K1 shield. Thus you could install the program, flip the orientation, and then see if the menu button works 'upside down'. If the button works, this points the finger to your hardware .... though if the square is properly going orange, something is clearly being noticed. If it doesn't work either, then we know a little bit more.
I thought that melly was talking about the button on screen where you walk around the NBZ. There is a left panel with the knight's face on the top and on the bottom a yellow slider. In the right panel, on the bottom is the button with 3 rectangles (which is the one that I think is being referred to), then a crosshairs button you can use to centre your knight, then the flag of the faction whose neighbourhood you are in, which you can also select, a gun button for inventory, a computer button to check your computer, and a right arrow or stop button to control your walking, and flip to a view of the whole neighbourhood, not just where you are.
All of these little button (aside from the flag) turn orange when you press them. And I am assuming that they work for melly properly, as the complaint wasn't 'all my buttons aren't working' just that one.
When I press that 3 rectangle button I get 4 more things to press. 'Center' 'Help' 'Options' and 'Quit'.
This suggests to me a work-around.
Center you can get with the cross-hairs, so already covered. You can put a link to the manual in a browser, and so get Help that way. Repeatedly pressing the back button will get you another way to quit.
So its the options that is the problem, and there is another way to get this, too.
Fire up the game so you get to the very first screen, the one that has a New Knight button on top, pictures of your most recent knights, and a 'More Knights' arrow. Under that is a wide button that says: Game Store. You may have to scroll the region to have this button become visible. And below that is:
a cogwheel button, a button that says Rules and an exit button.
If you press the cogwheel you -- ta dah! -- get to the Options section, and can change things there. Rules is another way to get the help file, so the other thing you might be missing if you cannot store the manual on the tablet somewhere a browser can reach.
Hope this helps, Grävling
phone: Huawei Y3ii LUA-L21 OS 5.1 Android EMUI 3.1 Lite Kernel 3.10.65 Build # LUA-L21C576B105. Android Security Patch 2016-03-01
Coolest Tablet Yet! (now rooted!) NVIDIA Shield Tablet K1 Android Version 7.0 (Nougat) Kernel Version 3.10.96+ buildbrain@mobile-u64-831 #1 Sat May 20 07:26:59 PDT 2017 NRD90M.1928188_904.2811 Shield Version 5.2 (24.29.404.153)