What if the connection is not established and the 2 RJ45 LEDs remain lit-fixed and the ARM-SE is powered on?

This indicates that the equipment connected to the ARM-SE is not at the right speed, in fact the ARM-SE supports a maximum speed of 10Mbps and this happens if it receives frames at 100Mbps for example.

In this case, you just have to set the speed of your equipment to 10Mbps or automatic. On a PC, you need to set the network card speed to AUTO.