Quicktime Screen recorder malfunction

I have updated my OS to Mojave (10.14.6) but since doing that, the QT (10.5) screen recorder will not accept a microphone either internal or external. I might have clicked by mistake "do not allow" right at the beginning but surely there must be a way of changing it?... when I do change it ...it brings up a warning triangle and will not record the screen,,, then "New Screen Recording",, is greyed out!.. If I shut the application and then re open... it goes back to not recording any sound... please help