Agree with BAR on that try it again, I turn green when I see guys have mis-fires and straight away open the bolt or re-cock the rifle with out waiting the mandatory 30 seconds without re-cocking always keeping the weapon safely pointed down the range.
Could be build up of crud inside the bolt plus the main spring may have lost tension over the years just gradually getting weaker until it wont fire the weapon, I always de-cock all my bolts then put them in separate pencil case holders.