I had the same issue, I found this post; Ionic Pro: Issue when git push for building where a guy basically adds to package.json;
"build:local": "ionic-app-scripts build",
"build": "true",
Just to warn you, I raised a ticket for an assumedly unrelated error Ionic Support said (bizarrely) that "you have configured your app to not run a build when you push to Ionic Pro." and pointed at the above text but it builds fine, I just can’t package the damn thing in Pro.