All devices working, syncing & connecting with iCloud except iMac (OS Sierra)

My iMac running OS Sierra is not connecting to the Internet ( either WiFi or Ethernet) nor syncing with iCloud.

I’ve reset PRAM & ran a Disk Utilities check to fix any hard drive problems but to no avail.

My iPhone iPad and MacBook all connect wirelessly via the same router and all devices sync files via iCloud without issues.

I’ve checked that the iMac is still

listed as a device in my AppleID profile

It is suggested elsewhere that typing the following into Terminal & restarting immediately may fix things? but I’m not that confident with Terminal commands..

killall bird <enter>

cd ~/Library/Application\ Support <enter>

rm -rf CloudDocs <enter>

Any help is appreciated!