Custom Search JSON API returns 403 despite enabled API, valid key, billing, metrics, and nonzero quota

Google Cloud Cloud Foundations & Onboarding
1

I am trying to use Custom Search JSON API / Site Restricted JSON API.

Additional context: this is not a newly created Google account or newly created Cloud project. The Google Cloud project is from 2023 and already had an existing API key before I created API key 2 for testing. I am trying to determine whether this project should be treated as an existing Custom Search JSON API customer/project, or whether Google is now denying JSON API entitlement despite the older project and existing key.

Custom Search API is enabled in my Google Cloud project. Billing/free trial is active. I created a new API key in the same project. Requests made with that key appear in Custom Search API Metrics and count against quota.

The hosted Programmable Search Engine page works, so the cx/search engine exists and is functional outside the JSON API path

Evidence:

  • Fake key returns API_KEY_INVALID, so the request path and API-key validation are working.
  • Real key reaches customsearch.googleapis.com and appears in Metrics.
  • The project is from 2023 and had an existing API key before this troubleshooting.
  • I created API key 2 only to rule out a stale/bad key.
  • Quotas are nonzero:
    • Queries per day: 10,000
    • Site Restricted Queries per day: Unlimited
    • Queries per minute: Unlimited
    • Site Restricted Queries per minute: Unlimited
  • Both API methods fail:
    • google.customsearch.v1.CustomSearchService.List
    • google.customsearch.v1.CustomSearchService.SiteRestrictList

Endpoint results:

/customsearch/v1 returns:
“This project does not have the access to Custom Search JSON API.”

/customsearch/v1/siterestrict returns:
“The caller does not have permission.”

The hosted Programmable Search Engine page works:

Cloud support will not allow me to file a technical support case because the account is on the free trial, and Billing Support live chat/email is also unavailable on the free trial.

Can someone confirm whether this project needs Google-side entitlement/reactivation for Custom Search JSON API / Site Restricted JSON API access?

2

Same issue here, and I have additional data points that might help narrow this down.

I spent several hours today isolating every variable and the 403 “This project does not have the access to Custom Search JSON API” persists across:

  • 4 separate GCP projects (including brand-new ones created today, with no org)
    • Multiple freshly-created API keys, restricted only to Custom Search API
      • 2 completely different Google accounts (one personal, no Workspace/org at all)
        • Billing linked and active on every project
          • No restrictServiceUsage org policy in place
            • Disable/re-enable of the API
              • The Google-hosted “Try this API” explorer on the docs page works fine with its own internal key and returns a normal 400 for a missing param, so the endpoint itself is healthy; this looks like a project/account entitlement issue on Google’s side, not a client-side config problem.
            • Also confirming the same support dead-end: no paid support plan, so technical cases are unavailable, and Billing Support only offers the Gemini Cloud Assist chat, which requires enabling extra APIs project-wide just to reach a human.
          • Would be great to get a Googler to weigh in, this looks like a broken/stuck entitlement flow for the Custom Search JSON API, not anything we’re doing wrong.