Big Problem with SystemSettings

Try using Activity Monitor to force the app to close:

1. In the Activity Monitor app  on your Mac, under the Process Name list, select the app or process you want to quit. An unresponsive process is marked with (Not Responding).
2. Note: The Process Name list is not available in the Cache tab listings. 
3. Click the Stop button  in the upper-left corner of the Activity Monitor window (or use the Touch Bar).
4. Choose one of the following options:

• • Quit: This is the same as choosing File > Quit within an app. The process quits when it’s safe to do so. If quitting the process could cause data loss or interfere with another app, the process doesn’t quit. 
• Force Quit: The process quits immediately. If the process has files open, you may lose data. If the process is used by other apps or processes, those apps or processes could experience problems.
  • To see if a process is used by another process, choose View > All Processes, Hierarchically.

If that doesn't help, try restarting your Mac. If you're unable to restart your Mac because of the app, press and holder the power button until your Mac shuts down. Make sure you save any documents you have open before forcing your Mac to shutdown.

This similar question. has been asked and answered from another similar question.

Suggest reading the reply from @leroydouglas for possible solution .

link below

unable to accept iCloud terms and conditi… - Apple Community

Use Option (or Alt), Command, Esc on the keyboard to force it to quit

Then Restart

If your Mac won't restart, force your Mac to turn off:

1. Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.
2. Turn your Mac back on.

If you can not turn off the " Find My "

refer to link below

Turn off Find My on your devices and items