https://wccftech.com/apple-macos-big-sur-download-issues-services-problems/

Several users have complained about Apple services such as iMessage, or even Apple Pay, not working for them. For those wanting to download and install the company’s major update for Macs titled macOS Big Sur, they’re experiencing problems with that too. Apple has apparently acknowledged the issue, with its employees working around the clock to ensure timely restoration of all services.

If you visit Apple’s System Status page to see which services are available for a wide range of products, you’ll be able to monitor why exactly your device or Mac aren’t functioning properly. One of those problems happens to be with the macOS Software Update tool. Considering that Mac owners all around the world wanted to experience what macOS Big Sur was all about today, this isn’t great timing for Apple at all.