Can't pull configuration from Realm

I wrote a GitHub Action, to update my production settings in realm (Schema/Functions/…). I did this so far manually from my machine. Since moving to GitHub Actions I get following error:

pull failed: (403 Forbidden) Please check your Atlas API access list entries to ensure that requests from this IP address are allowed

As I don’t know the IP address of my current GitHub Runner, I cannot whitelist the IP Address in my API Key. The address is also not allowed.
Is there a way to allow my GitHub Runner to access my project?

This is the line throwing the error:

realm-cli login --api-key="${{ secrets.REALM_API_PUBLIC_KEY_PROD }}" --private-api-key="${{ secrets.REALM_API_PRIVATE_KEY_PROD }}"

cd ${GITHUB_WORKSPACE}/app-services
realm-cli pull --remote="${{ secrets.REALM_API_NAME_PROD }}" -y --local myProject-prod

Strangely, pushing works, which confuses me even more. Anyone has any idea why pushing works and pulling does not? How can I deal with the problem of my unknown GitHub Runner IP ?