Mac: Magic Mouse not connecting, keyboard issues

Based on the symptoms described, there are a few possible causes and troubleshooting steps we can try.

What could be causing these issue:

• Bluetooth may be disabled or not functioning properly.
• The Magic Mouse may not be paired with the iMac.
• The keyboard may have lost its Bluetooth pairing.
• Battery level may be low.
• If the Mac was recently set up, there may be a problem with the wireless device pairing process.
• Low batteries, charging problems, or a fault with either the keyboard or mouse.

With that said, here are a few things you can try:

• Verify both the Magic Mouse and keyboard are powered on and sufficiently charged.
• Connect the Magic Mouse directly to the iMac using a USB-C charging cable (if available) and allow it to pair automatically.
• If possible, connect the keyboard via cable or use a temporary USB keyboard to regain access to System Settings.
• Restart the iMac and test both devices again.
• If a wired keyboard is available, navigate to:
  • System Settings > Bluetooth
  • Remove and re-pair the Magic Mouse and keyboard.
• Test whether the keyboard functions at the login screen or during startup to determine if the issue is system-related or hardware-related.

There wasn't much in your post that we could go on. As such, please provide the answers to the following:

• Is this a new iMac or an existing system that previously worked?
• Are the keyboard and mouse Apple Magic devices or third-party devices?
• Does the keyboard work at the login screen or only fail within System Settings?
• Are there any error messages when attempting to connect the Magic Mouse?