Macbook doesn't goes to sleep mode

First, open "System Preferences" from the Apple menu or the dock on your MacBook Air. Then, navigate to the "Energy Saver" preference pane. Here, you'll find options to control when your Mac goes to sleep and when the display turns off.

In the "Battery" tab, make sure that the slider for "Turn display off after" is set to a reasonable duration. This setting determines how long the display will remain on before it turns off when the MacBook is idle on battery power.

Next, switch to the "Power Adapter" tab and adjust the corresponding slider to specify how long the display should remain on before turning off when the MacBook is connected to a power source.

Additionally, ensure that the checkbox for "Put hard disks to sleep when possible" is checked in both the "Battery" and "Power Adapter" tabs. This option helps conserve energy by putting the hard drive to sleep when it's not in use.

If these settings are already configured correctly and your MacBook Air still doesn't enter sleep mode or turn off the screen when you close it, there may be other factors at play. In such cases, it's recommended to reset the System Management Controller (SMC) on your MacBook Air, as issues with power management can sometimes be resolved by resetting the SMC.

To reset the SMC, shut down your MacBook Air, then press and hold the "Control," "Option," "Shift," and power buttons simultaneously for about 10 seconds. Release all keys and buttons, then press the power button again to turn on your MacBook Air.

If the issue persists after adjusting settings and resetting the SMC, consider reaching out to Official Apple Support or visiting an Apple Authorized Service Provider for further assistance and diagnosis of the problem. They can provide additional troubleshooting steps and recommend appropriate solutions based on the specific circumstances of your MacBook Air.