The ETH STS should either be on Solid indicating Communications OK or a pattern of flashing/pause/flashing. If it is off this would indicate a hardware issue.
Below are the flash pattern descriptions.
2 flashes - Invalid MAC address
3 flashes - No link; Incorrect/no cable connected or no valid device at the other end of the cable.
4 flashes - Duplicate Ip address; Make sure that you did not inadvertently set the PC/Laptop to the M340 address.
5 flashes - Waiting for a Served IP address; Either the switch on the back is set for Boot P or the project is configured for 'From a Server' and nothing is serving.
6 flashes - Default Ip; This probably means that the switch on the back is set to Clear IP or Disabled. No Ip address has been assigned. https://www.se.com/us/en/faqs/FA213636/
7 flashes- Probably means that the switch is set to Stored but the projects Eth network was not bound to the Ethernet port. (or any other Rotary Switch/Internal config conflict) https://www.se.com/us/en/faqs/FA233493/