Gemini API: 401 Unauthorized despite billing active and key restricted

Project: (PII Removed by Staff)
API: Generative Language API (gemini-1.5-flash)
Error: 401 Unauthorized

Steps taken:

  • Activated full billing account
  • Enabled Generative Language API
  • Deleted old key, created new key restricted to Generative Language API
  • Verified quotas (Requests per minute > 0)
  • Tested with PowerShell using correct endpoint (generativelanguage.googleapis.com)
  • Key starts with AIza… and copied directly from console
  • Still receiving 401 Unauthorized after >1 hour

Request:
Please confirm if there are additional restrictions for activated accounts in India, or if there is a backend issue preventing Gemini API from accepting API key authentication.