And provide new features, it's important to always be running the most recent version of macOS on your machine. Not all macOS upgrades bring good news, either. In addition to being a startup problem, they might cause your Mac to crash often.

This page summarizes the three best methods to try if you upgraded to a newer OS on your Mac. Such as macOS Catalina or mac 11 Big Sur Beta, but now your Mac won't switch on.

1. Inspect the power supply.

It's possible that the battery in your Mac, especially if you have a Mac laptop, is dead. Therefore, after recharging the Mac for a few minutes, the first thing to do is to verify the power connection. And then start the Mac by pressing the power button.

2. Revert to an older version of macOS

A reversion to a more stable version of macOS, like as macOS Mojave, is your best bet if the latest update to your Mac's operating system is causing problems. Be sure to back up your Mac's hard drive before you downgrade from macOS Catalina. The hard disc must next be formatted using APFS or macOS Extended. And completely erased before the downgrade can begin.

Revert to a previous version of macOS (Mojave) in four different methods.

If you purchased your Mac with macOS Mojave already installed, you may reinstall macOS through macOS Recovery.

• Restart your Mac and hold down the Command + Option + Shift + R keys until the Mac prompts you to do so.
• When prompted by a loading screen, you may release the keys.
• After clicking Continue in macOS Utilities, choose the option to Reinstall macOS.
• Make sure your Mac doesn't go to sleep or shut down in the middle of it by following the on-screen directions.

If you have already made a Time Machine backup of your Mac, you may use it to restore your Mac.

• Press the Command + R keys together as soon as the Mac restarts.
• Hold out on letting go of the keys until you see the Apple logo.
• Link the data storage drive to the Mac.
• In macOS Utilities, choose Restore From Time Machine Backup and then Continue.
• Choose the disc you want to use for the backup, and then press the Next button.
• Go to your most recent backup and choose the file you want to restore.
• Until the Mac returns to that backup, please be patient.

Utilize an APFS snapshot in macOS Recovery.

• After restarting, hold down the Command + R keys until the login screen appears.
• Hold out on letting go of the buttons until you notice the Apple logo.
• In macOS Utilities, choose Restore From Time Machine Backup and then Continue.
• Choose the disc you want to use to boot the computer, and then click Next.
• To proceed, click on the most recent picture.
• Just wait till it's done, and do what it says on the screen.

Reinstall macOS Mojave from a disc image. Here you may discover a comprehensive instruction provided by Apple Support.

3. Mac hard drive repair is Option

Changes to the file system, user interface, and overall layout of macOS may occur during the upgrade process. In the worst case scenario, the update might corrupt the data structure and file system. If you have issues on your Mac while updating, checkout https://perfectpcserver.com/ to get a solution.  The Mac can't go through the startup process because of this.

The First Aid feature in Disk Utility can be used to fix a damaged startup disc, although it's usually ineffective. You have nothing to lose by giving it a go.

• You may accomplish this by restarting your Mac and holding down the Command + R buttons as soon as Mac wakes up.
• Hold out on letting go of the keys until you notice the Apple logo.
• Disk Utility may be accessed through the Utilities' menu in macOS.
• Choose the disc you want to boot from on the left and then select "First Aid."
• Select Run when the prompt appears.

Conclusion

Downgrading to an older version of macOS might be helpful if you run into issues after upgrading to a newer OS. Since your Mac is malfunctioning, it is imperative that you take immediate measures to secure sensitive data.