Most probably issue is with iCloud Keychain , reset iCloud Keychain https://support.apple.com/en-in/HT202755
Also sometimes if you change the read and write permissions in home folder , shared , guest folder or change the date and time settings , alter location services and if you sign out incorrectly from system preferences > iCloud this error shows .
Click on finder > Go > hold option key > click on library > find a folder preferences > from the preferences folder drag and drop com.apple.systempreferences.plist to the desktop , restart the Mac and again open the browser for few minutes , if the error still occurs contact senior care apple advisor see this link https://support.apple.com/en-in/HT201232