The issues in macOS Catalina:

• The failure of macOS 10.15 to download is a regular macOS Catalina issue, with some users receiving an error message stating 'macOS Catalina download has failed.' Others, on the other hand, are getting error messages saying 'The network connection was lost' when trying to download macOS Catalina.
• Furthermore, when downloading and installing macOS Catalina, many people have complained about the download ending at roughly 511.5MB and the machine displaying a 'gateway timed out' or 'bad gateway' error.
• Readers have reported that after installing macOS Catalina, their Macs display the 'Setting Up Your Mac' message but do not do anything else. You'll need to restart your Mac or MacBook if this is the case. Don't worry; the 'Setting Up Your Mac' notification indicates that the update is complete, and restarting your Mac will not cause any data loss or damage.
• If you're having difficulties getting into your Mac or MacBook after installing macOS Catalina, or if you're trapped in a loop of signing in and then logging out, the methods below may assist.
• To begin, restart your Mac while holding down the Command + S buttons on your keyboard. You'll be thrown into a loop if you do this.

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