Distributed Authority intermittent client connect failures

Based on Forum-Issue-1717323 with a continued internal discussion here.

Description

I’m seeing an intermittent failure when starting a Distributed Authority session with Unity Services Multiplayer + NGO + UTP + Relay.

To debug it, I embedded the com.unity.services.multiplayer package locally so I could add instrumentation inside the package and also added a few traces in com.unity.netcode.gameobjects / Unity Transport. That let me compare a good run and a bad run at a fairly low level.

What happens in the good case:

• Lobby/session setup completes normally.
• Distributed Authority session creation succeeds.
• Relay join/allocation succeeds.
• UTP starts as client.
• Relay reaches Established.
• Relay layer receives Accepted.
• NGO then gets Connect / ClientConnected and the session proceeds normally.

What happens in the bad case:

• The flow is identical through lobby setup, Distributed Authority session creation, relay join/allocation, and UTP client startup.
• Relay also reaches Established.
• But the relay layer never receives Accepted.
• The client keeps sending connect requests until UTP eventually disconnects with MaxConnectionAttempts.
• NGO then reports client disconnected / startup canceled.

A few notes from instrumentation:

• Region resolution is the same in both runs.
• Distributed Authority session creation and relay allocation both succeed in both runs.
• The divergence seems to be specifically after relay establishment, in the Distributed Authority/approval/accept path.

So the failure appears to be:

• not lobby/session creation
• not region selection
• not relay allocation/join
• not basic UTP startup

It looks more like “relay established, but the connection is never accepted/approved”.

Has anyone seen this before, or does this pattern point to a known issue in the Distributed Authority/Relay/NGO handshake path? In particular, is there a known reason why a client would reach Relay Established but never receive Accepted, eventually failing with MaxConnectionAttempts?

Initial setup
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Reproduction steps
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Expected behaviour
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Actual behavior
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Logs and Links
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