Main power cable disconnected from one of the LPS units.

Check if the main power cable is connected with the “MAINS INPUT” socket of the LPS unit.

Disconnected wire unit between the “CTRL IN” and “CTRL OUT” sockets of the LPS units.

Reconnect the wire unit between the “CTRL IN” and “CTRL OUT” sockets of the LPS units.

Malfunction of one of the LPS units. The red LED “ERR” of the malfunction LPS unit flashes fast.

Replace the whole LPS module. See "Removal of an LPS module".