Apple Watch series 3 cannot update

why I get the message of my mobile iPhone 6s Plus - it is updated to the latest iOS 13 version- is not connected to the internet when I try to update my Apple Watch series 3 although my mobile is connected to my home WiFi and connected to its charger and my watch is fully charged and is connected to its charger and no action but restart over or try again and nothing is working except unpairing my watch and start an infinite loop without being able to use my watch ?