Hiya, sorry you are having trouble with your build.
This Support Guide contains a ton of useful debugging tips that can likely help you solve your problem 
Additionally, this Support Guide houses all of our resources for debugging build and deploy issues.
We also recommend trying to search the forums with the build error you encountered - it’s likely your question was already asked by someone else!
If you are still having problems, please provide as much information as you can on what you have already tried, what your build settings are, a full copy of your most recent deploy log, your package.json, etc. Thanks!