The most common reason is the date on your Mac is incorrect—this often happens when recovery mode sets the date back to something like 2001 or 2017. Other possible causes are expired installer certificates, damaged installation files, or using an old version of the macOS installer. Now that you know what can cause the error, let’s go through the steps to fix it. Remember, as mentioned earlier, sometimes a simple restart is enough, so try restarting your Mac before moving on to the next steps. If the error keeps showing up even after a reboot, continue with the methods below.
1. Change Date and Time
When you install or upgrade macOS, the installer connects to Apple’s servers. These servers check that your Mac’s date and time are accurate. If the settings are wrong, the connection is blocked, and you get the error message. To fix this, you’ll need to set the correct date and time before trying the installation again. There are two ways to do this. If you can use your Mac normally, you can update the date and time from System Preferences. If you can’t start up your Mac as usual, don’t worry—you can still change the date and time from macOS Recovery. Follow these steps:
2. Use macOS Recovery
Another way to solve this problem is with macOS Recovery. When you start your Mac in macOS Recovery, you have options to install different versions of macOS, depending on which keys you hold down. Here are the key combinations you can use—pick the one that suits your needs:
3. Download Installer Again
If none of the above methods fix the issue, it’s possible that the installer you’re using is corrupted or incomplete. This happens sometimes if the download is interrupted. The best solution here is to delete the existing installer from your Mac, then download a new installer from the official source. Once you have a fresh installer, try the installation process again—this should solve the problem.
