Can't move cursor location by double click

Can't move cursor location by double click

I am not technical so please forgive me if I do not use the proper terms.  I am having an issue where I can no longer double click in the body of an email and get my cursor to move to that location.  I am only able to move the cursor by using the arrow keys.  It will also no longer allow me to highlight sections of my text for deleting and etc.  Any help would be appreciated.