interesting would be, what have you focused (where is caret) while you press hotkey.
it might be possible that something got focus that eat all your hotkey tries.
what i meant to say, from programmers point of view, a program can override a hotkey in its own thread/process.
mousers wonderful screenshot app set global hotkeys, such can be blocked/reassigned/overwritten from within other applications.
thats why it would be good to know what is focused/got caret when pressing hotkey. this would give a reproducable clue i hope.
terminating other applications that you started after screenshot capter was loaded, one by one to find the disturbing enemy, that would i also try.