Well, after trying again for a while, it just worked.
I have a wild guess that the service can be too loaded at times (too many users trying to build at the same time), making the build fail.
Even so, it is a little bit frustrating not to know what’s happening.
EDIT : and then after using build:status : “There was an error with this build”
ID : 8e1f10b0-362c-4416-8b14-589cc4734ca0
EDIT2 : another one, 2 hours later : 18c57d00-1b2e-401d-9ce5-6038b580fed0
Nvm, @coldk, looks like the errors were transient. Just re-ran your build and it succeeded. Go ahead and grab the link to your IPA with exp build:status