Someone who is trying to help answer your question will give you this link if you have posted an error log which they believe would let you know the error - if you take the time to read it carefully.
While they could have told you exactly what the problem is, this will not help you as a developer as much as learning to to find and read error messages for yourself. Developing this skill will allow you to find and fix your own problems in future - this is a fundamental skill in software development.
You will get much better help (and respect) if you do this.
Also, it is considered a basic sign of respect towards those who are volunteering their time to help you, for you invest the time to really try to read and look for clues in an error report, before asking for help.
Take your time
Read the error message(s) from start to finish
You maybe won't understand all of it - this is normal.
Make sure you are looking through ALL of it
Look for clues:
sections of your code
names of YOUR files and line numbers of them
timestamps (if any) that tell you WHEN something happened
Spend at least 5 minutes doing this
Make notes of clues, if you do not find your answer immediately
What the error was
What the relevant part of the error message was that describes the error, so that you are more likely to recognise it in future. You will find that the same error messages come up time and time and time again.