EDIT: Generalized troubleshooting steps are listed in this doc, and are a good place to start if you don't understand how or why your build failed: https://docs.microsoft.com/en-us/appcenter/build/troubleshooting/build-failed
Try running a build with Distribute turned off.
Building in release mode locally and see if the issue still occurs.
If that doesn't work, take the following actions and contact customer support:
Download your logs.
Upload your logs to the chat window (Paperclip Icon) or include them in an email.