Production build fails due to admob

I have tested my app with real device (iOS). Now I need to publish it.
Publishing for iOS is not well documented so Im following a few different guides.
One of the guides (the officiale one: states that you should first run this command:

ionic package build ios --release --profile PROFIL_TAG

When I did it, I didnt get any error. The output was:

Your app has been successfully submitted to Ionic Package!
Build ID: 1
We are now packaging your app.

The I wondered what that means. Ionic server is packaging my app? It seems you can run the command

ionic package list

to see current status of the app that is going to packed.

Here I got bad news. Under the column “STATUS” I saw “FAILED”.
The output also contained more details:

Error: Registry returned 404 for GET on

Great. I have been struggling with admob and finally I made it work (during development). And I dont really remember which steps made the trick. But, in development, admob works now. And I can see ads show up in the app.

But now, again, I get the old bad error:

Error: Registry returned 404 for GET on

Very frustrating. Anyone that has exeperienced same issue?