Session stuck showing "Can't reach your computer" when resuming existing conversation, while new conversations connect fine

When resuming an existing conversation in the Claude Code desktop app, the session gets stuck with:

"Can't reach your computer — It may be asleep or offline. This session will reconnect when it's back."

The message never clears while sending is stuck ("Sending..."). Opening a brand-new conversation on the same machine works fine and connects immediately — only resuming a prior session hits this state.

Environment:
- Platform: Windows 10 Pro (10.0.19045), win32
- Client: Claude Code desktop app (Code tab)

Expected: resuming an existing conversation should reconnect to the local machine the same way a new conversation does, without getting stuck in an unreachable state.