iPad Viewer appears to be in permanent VIEWER mode only

I am new to using NVC viewer on my iPad i have a couple of target systems set up and appear to work OK, But, if I try to select any element on the target Desktop nothing happens. 

One one of my target systems which is a Raspberry Pi the desktop is actually active with Python screen, on this device i can move the cursor within the Python app but have absolutely no other control of the Python app or the desktop. I cannot select any item in the main menu.

My setting within VNC appear to be correct in that i have Mouse control selected and the View only option is NOT selected.

Any ideas please?

Thanks

JohnW