This is likely an issue with Wi-Fi … some people experience dropouts and unreliable connnections with Big Sur. You could Google–I prefer to DuckDuckGo–for a possible solution or recreate the Wi-Fi configuration by following the following steps. Also, please note that for best results your Core should use a wired connection.
- Turn off Wi-Fi on your Macbook
- Open Finder and press
G - Type
/Library/Preferences/SystemConfiguration/in the box and hitEnter - Select the following files:
- NetworkInterfaces.plist
- com.apple.wifi.message-tracer.plist
- com.apple.airport.preferences.plist
- preferences.plist
- Move these files to your Desktop
- Restart the Macbook
- Re-enable Wi-Fi
You can delete the files on the Desktop is the problem is resolved or unchanged.