How do I know if the deployment failed? Look at the EVENTS tab, you will see your last deployment action. If you have a pink FAILED flag on the right, then it has failed.
At that point, you don't know why or how to fix it and the impact on your infrastructure. The best action is to click on this event, it will show you the failure details. For example :
Then you need to debug the error yourself until the deployment is successful.
After a successful deployment, you need to clean up your build folders.
In some cases this is caused by composer.(json|lock) files that could not be executed or do not have the correct permissions.
If necessary, you can always ask support for help.