FLEX-6300 blinking green forever

I have had this unit for many years in the same setup. No changes ever. I use it sporadically. I used it just yesterday without problem. I never leave it (or the power supply - Astron VS-50M) on when I'm not using it.

Today, after I pressed the start button the green light blinked as usual. I expected it to go solid after the usual 20-40 seconds. This time, it never stopped blinking.

I've tried the "5-second-hold-and-go-to-blinking-white-and-release" procedure a few times. Each time - after the white blinking stops - the forever green blinking continues.

Any ideas about how to fix this would be appreciated.