This is a CNC milling machine with Rexroth PLC and HMI,there were power cuts for few times and now when the machine started HMI display shows that connection interruption. what could be the reason for this?
check the communication cables between the controller and HMI.
follow the proper shutdown procedure for the controller and check earth to neutral voltage is less than 3Volts then start power on your machine and try.
hope due to multiple power shutdown your Rexroth controller program might be corrupted.
Get the program from machine OEM and reload it.
If there is no program in your controller it will never communicate with HMI