WhatsApp Business API: 'Unsupported post request' error persists with full permissions

Question

Issue: Getting 'Unsupported post request' error when accessing /accounts with WABA_ID despite having all required permissions:

• whatsapp_business_messaging
• whatsapp_business_management
• Tech Provider verification
• Full business verification

Error: 'Unsupported post request. Object with ID '[WABA_ID]' does not exist, cannot be loaded due to missing permissions.'

Tried:

• New phone numbers
• Fresh access tokens
• Different WABA_IDs
• Permission resets

Note: Can successfully send messages via API, but contacts API access fails. Request format appears correct, but permissions seem blocked despite having all verifications.

Meta support directs all technical issues to their Developer Forum, but the forum throws a ReactComponent error, making it inaccessible. Left without official support channels to resolve this.