I want to use the FEC function. When I connect the two pairs of ports of the two switches with two wires at the same time, I find that each switch is always a normal port and the other port shows a red light. Is the switch port faulty?

In general, this situation switch is normal, because the two switches are connected by two ports, so the switch thinks that there is LOOP, it automatically disconnects one of them and drops the corresponding port Down (the port showing the red light). The solution is: turn on the function of Spanning-tree (it is turned on by default), and let the switch know that these two ports are functions of FEC, which is logically a port.