Most common cause
A failed build is usually caused by something specific inside your project, an invalid value in a block's settings, or a block still referencing something (a screen, a variable) that was since deleted elsewhere in the project.
What to check
- Open your project and look for any warning indicator on individual blocks, these flag exactly the kind of invalid or dangling reference that breaks a build.
- Fix whatever's flagged, then re-run the build.
This resolves the large majority of build failures, since it's almost always something concrete inside the project rather than an infrastructure issue.
Still failing with no obvious cause?
Reach out with the project name and roughly when you tried building, that's enough for us to look at what actually happened on our end.