why can't I open LibOffice on my mac book air

can not open my LibreOffice on my mac book air

And you have

  • upgraded to Big Sur (macOS version 11.0.1)?
  • installed LibreOffice version <7 ?

If “yes” to both questions - install LibreOffice 7.0.3 and write a nice letter to Apple.

So what? Well, throw out that trash and buy an ASUS or HP (LibreOffice works fine on both). Or read these guidelines and ask a good question (pay attention to Opaque’s comment).