New iTunes connect interface error "You must choose a build"

You have to upload a binary for your new App. Then, you wait ~5-20 min while processing and select the plus button and select a binary and save. After that you may Submit for Review. If it takes longer than ~25 min try uploading the binary again.

I uploaded a binary and still I cannot choose it.

When I clicked on Prerelease I could see that the binary is listed and when I pointed to the ? it says

After builds are uploaded they will go through a processing status before they can be used.

So I guess Apple has introduced a new step into the process, and we must wait for it to complete.

I had the same issue: The Add link was not visible using Firefox v32. My solution might work for others as well:

1. Inspect the DOM with your browser developer tools and locate the anchor element in the DOM with the inner text Add.

2. For this anchor elmenent, remove all classes (text in the element's class attribute, that is), in order to make the element visible in the browser.

3. Click the add link.

4. Choose the binary you've (probably) already uploaded.

5. Click save in the top right corner, then Submit for review.

Pretty hard core that you have to hack the DOM in order to submit an app!