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).