I cannot sign into icloud and system preferences is not responding - how do I force quit

When you open your web browser pop - ups are showing to enter login password and you are not able to connect to iCloud .

For I cloud issues use this article : Get help using iCloud Keychain - Apple Support

On your Mac:

1. Choose Apple menu > System Preferences. Click iCloud, then select Keychain.
2. When asked to enter your iCloud Security Code, click Forgot Code.
3. Click Reset Keychain to replace your iCloud Keychain in the cloud with the iCloud Keychain items on your Mac.
4. Click Reset to confirm. You'll be asked to create a new iCloud Security Code.

And regarding your the prompt of entering login password multiple times .

If keychain is prompting to enter password multiple times , & pop - up is not going away when safari is opened .

In user library click on go to go folder & type ~/Library then find a folder > keychains > remove first folder ( alfa numeric folder ) to trash . Restart & empty the trash , go to internet accounts & once again configure web mail account , I cloud mail account by entering their passwords .

Open air port utility via spotlight > enter your base station password .

And , also system preferences is not responding open activity monitor via spotlight , take the cursor on top menu bar > view > click on windowed processes > if you see system preferences ( written in red colour , system preferences not responding ) , select it > go to force quit > quit system preferences .

Also it , is recommended enter in your user library ( click on go > to go folder and type ~/Library , find a folder preferences right click on com.apple.systempreferences.plist to the desktop .

Restart the machine , open safari and browse for few minutes , then again go to the user library , new plist of system preferences , is created - just monitor , then you can delete the system preferences plist that is on the desktop into the trash , again restart the system and empty the trash .

As corrupted plist must not be in the trash .

If you continue to have problems with System Preferences, it might be a corrupt .plist.

Do a backup, preferably 2 backups on 2 separate drives.

Quit the application.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Select Library. Then go to Preferences/com.apple.systempreferences.plist. Move the .plist to your desktop.

Restart the computer, open the application, and test. If it works okay, delete the plist from the desktop.

If the application is the same, return the .plist to where you got it from, overwriting the newer one.

Thanks to leonie for some information contained in this.

To Force Quit go to the Apple logo, top left, and scroll down the panel to Force Quit.