iOS Google Tag Manager integration - Can not retrieve container from network. Response: 404

I follow documentation about adding Google Tag Manager into project https://developers.google.com/tag-manager/ios/v5/. I added container folder to my project's target but I am still getting some warnings from GTM to log and it is not possible to track events to Firebase.

GoogleTagManager warning: Can not retrieve container from network. Response: 404 GoogleTagManager warning: Event emitted before runtime was initialized.

What is the proper way to initialize Tag Manager? I use my "containerName" + .json as name of the container file and add them to folder "container".

GTM iOS SDK 7.1.1

Thanks.

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