WAHA session shows WORKING, but messages fail (ack = -1). Why is session state inconsistent and how should it be handled?

[MaxSapeiko]

Hi,

I am experiencing a critical inconsistency between WAHA session state and actual message delivery behavior and would like clarification on expected behavior and recommended handling.

Issue description
I using WAHA (WEBJS engine, version 2026.1.3) in production for sending WhatsApp messages.

Observed behavior
From last week (has been working well for the last six months) I see the following inconsistent states:

1. Session status

• Session is reported as: WORKING
• No QR required
• No disconnect events visible

2. Send API response
   sendMessage returns success response (no errors)
3. Message delivery behavior

In webhook I see:

• ack = -1
• ackName = ERROR
• isSendFailure = true
• Message is not sent at all via WhatsApp Web

Key issue
Despite all of the above, the session remains in WORKING state throughout.
This creates a misleading condition where:
The system appears healthy, but message delivery is actually failing or silently broken.

Received webhook (shortly):

{
  "event": "message.ack",
  "engine": "WEBJS",
  "environment": {
    "version": "2026.1.3",
    "platform": "linux/x64"
  },
  "payload": {
    "fromMe": true,
    "source": "api",
    "ack": -1,
    "ackName": "ERROR",
    "hasMedia": false,
    "_data": {
      "type": "chat",
      "ack": -1,
      "isSendFailure": true
    }
  }
}

[MaxSapeiko]

Account-specific ACK=-1 after session recreation

We have narrowed the issue down significantly.

Facts:

• WAHA version: 2026.5.1 (updated)

• Engine: WEBJS

• Session status: WORKING

• Messages sent through WAHA receive:

  • ack = -1
  • ackName = ERROR
  • isSendFailure = true

Additional testing:

• The affected WhatsApp account can send messages normally using the official WhatsApp mobile application.
• We completely recreated the WAHA session (logout, QR re-scan, fresh session).
• The issue persists after session recreation.
• Sending a simple manual text such as "Hello, this is a manual test message" also fails with ack = -1.
• A different WhatsApp account connected to the same WAHA instance, same server, same Chromium installation, and same WAHA version works correctly and receives ack = 1 (SERVER).

This suggests that the issue is account-specific rather than infrastructure-related.

Questions:

1. Have you seen cases where a WhatsApp account remains fully functional in the mobile app but all messages sent through WhatsApp Web / WAHA fail with ack = -1?

2. Does ack = -1 correspond to any known WhatsApp account restriction or WhatsApp Web limitation?

3. Is there any additional diagnostic information available from WAHA or WEBJS that could reveal the actual send failure reason behind ack = -1?

4. Can WhatsApp selectively restrict WhatsApp Web sending capabilities for an account while keeping the account otherwise functional?

Any guidance would be greatly appreciated.