In 2017 I got a call from someone saying "the system's down". It was code I'd deployed for them in 2002. Crazy reviewing some of that code. Some was really good, some was... not so much. :)
My favorite on these old systems...."Your software has a bug"
No, at this point there might be some un-anticipated behavior but most likely there is either a piece of hardware going bad or you have changed your procedures and are no longer using the software the same way.
