Block remote input feature suddenly stopped working.

Hey guys.   I have mom whos really bad with computers and i help her  remotely time after time with updates ,  cleaning , settings, checking for viruses and so on.  I often used block remote input devices feature to prevent her from interrupting me but recently that  function greyed out and i cant use it anymore. Its grayed out and when i click on it i have message like this feature is unavailable for you.   I  never updated versions on my or her laptop , last time i connected like 2 month ago and it worked just fine.   Any ideas ?