One of my mentors once gave me a list a obvious things to check when stuff doesn't work. Funny, years later I still need this list:
1. It worked. No one touched it but you. It doesn't work. It's probably something you did.
2. It worked. You made one change. It doesn't work. It's probably the change you made.
3. It worked. You promoted it. It doesn't work. Your testing environment probably isn't the same as your production environment.
4. It worked for these 10 cases. It didn't work for the 11th case. It was probably never right in the first place.
5. It worked perfectly for 10 years. Today it didn't work. Something probably changed.
One of my mentors once gave me a list a obvious things to check when stuff doesn't work. Funny, years later I still need this list:
1. It worked. No one touched it but you. It doesn't work. It's probably something you did.
2. It worked. You made one change. It doesn't work. It's probably the change you made.
3. It worked. You promoted it. It doesn't work. Your testing environment probably isn't the same as your production environment.
4. It worked for these 10 cases. It didn't work for the 11th case. It was probably never right in the first place.
5. It worked perfectly for 10 years. Today it didn't work. Something probably changed.