Help with an ancient digital timer

Yesterday I was going to shut off the filter with my timer. I always shut it off with the manual override versus the breaker box. Well yesterday the manual override did not work, it would not shut off in any mode, (program, manual, etc.). I changed the time to go off at 5PM and when I came home at 10 it was still on. It states that the display will blink when you've done the last step however mine did not blink at all. I'm hoping it's just a matter of new battery, if not....any ideas???? I called the company but this is so old that no one had any info on it. If anyone knows about this kind, it's a BRK Electronics 24 Hour Electronic Time Switch. Model # TS212R

If the company doesn't know . . . you're probably out of luck.