Debug This Error

I'm getting this error in my [language/framework] application:

ERROR:
[Paste the complete error message and stack trace]

RELEVANT CODE:
[Paste the code where the error occurs, with surrounding context]

WHAT I'VE TRIED:
1. [First thing you tried]
2. [Second thing you tried]

ENVIRONMENT:
- [Language] version: [X.X]
- [Framework] version: [X.X]
- OS: [Operating system]

The error happens when: [describe the trigger]
It started after: [any recent changes]