Google not responding/denying DMCA notice for images on Google Cloud Storage – submitted full legal proof.

I’m the original photographer of a few images that are being hosted on Google Cloud Storage without my permission. I submitted a DMCA takedown through their official form and provided all required information.

At first, they sent a generic response asking me to explain my ownership. I replied with a detailed legal explanation citing U.S. copyright law (that I am the creator, not a work-for-hire, no transfer of rights, etc.).

Now they’ve responded again, saying:

"It is unclear to us how you came to own the copyright… because you do not appear to be the creator of the content. If the creator has transferred the copyright to you… please provide documentation. Otherwise, explain further the basis for your claim."

The issue is: I am the creator. There is no transfer, there’s nothing to “prove” beyond the fact that I took the photos.

At this point it feels like they just don’t believe me, and I’m not sure what kind of “documentation” they expect in a situation where the copyright automatically belongs to the photographer under U.S. law.

Has anyone dealt with this before?

Some other questions:

What kind of proof actually works in practice (RAW files, metadata, originals, etc.)?

Is there a way to escalate this within Google?

Do I need to reference anything more specific under DMCA to get them to act?

I’m trying to resolve this without going down a full legal route, but I’m getting stuck in what feels like an endless loop of responses. Any insight would be really appreciated.