During my most recent flight, the "L REV ARMED" indication on the EICAS did not display after I armed both reversers, however "R REV ARMED" did display. Cycling the switches did not help. All the hydraulic switches were in AUTO, all generators were on, and everything was good to go. Both displayed upon takeoff from CVG, I'm fairly sure. This is the first time I've ever had this issue.   However, both reversers did deploy upon landing, as shown in the pictures.   Using the lat