MacBook Air won’t restart

Try booting into Safe Mode. If this works, then uninstall Intego by following the developer's instructions since anti-virus apps, cleaning/optimizer apps, and third party security software are not needed on a Mac and usually causes more problems than they solve.

macOS already has great built-in security especially when the user also practices safe computing practices as outlined in this excellent article written by a respected forum contributor:

Effective defenses against malware and other threats - Apple Community

"MacBook Air won’t restart: Tried to run an Intego update and had to shutdown to finish install. Now MacBook won’t restart. What to do?"

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Troubleshoot the MacBook Air's Power:

A. Black Mac Screen:

Go Here: If your Mac doesn't Turn On or Start Up - Apple Support

Using External Devices: Try Resetting the SMC and NVRAM, but this time, using an external keyboard. Connect an external monitor and see if you get an output.

B. Mac Power Issues:

Try a New Charger:

If it is currently charging from a charger, then use a new charger:

• Power & Cables - Mac Accessories - Apple - Select "Mac Compatibility" on the left
• Find the right power adapter and cable for your Mac notebook - Apple Support

A Few Links to Refer to Power:

• If your Mac doesn't Turn On - Apple Support

• How to Turn your Mac On or Off - Apple Support

• About Mac Notebook Batteries - Apple Support

• Charge the MacBook Pro Battery - Apple Support

• If your Mac Battery won't Charge - Apple Support