Hi,

Hello saikrishna9,

Can you go to “About This Mac” from the Apple menu and provide your exact model name? Depending on if you have a MacBook Pro, MacBook Air, or a MacBook will determine if your laptop is compatible for any macOS beyond High Sierra.

macOS Big Sur is compatible with these computers - Apple Support This is the most recent macOS.

If it turns out your device cannot install macOS Big Sur you may still have an update option from the previous versions.

How to get old versions of macOS - Apple Support. Each has different hardware requirements.

I hope this is helpful.

Download Mojave or Catalina from the link Scott posted. All Mac models other than the desktop Mac Pro have the same model-year requirement for them.

(200685)

Please tell us specifically what is or is not happening. What messages are you getting? Specifically what year and model Mac do you have? The link below will help you respond.

Writing an Effective Apple Support Communities Question - Apple Community