Why does my IBKR RTD formula in Excel show #N/A?

[streamxls-dev]

A question people ask in IBKR trading forums — answered here so it's searchable.

[streamxls-dev]

#N/A from any =RTD(...) formula generally means Excel could not reach the RTD server or the server has no current value. The usual causes, in order of likelihood:

1. The RTD server isn't registered or Excel can't create it — reinstall, and make sure Excel's bitness matches what the server supports.
2. TWS / IB Gateway isn't running or isn't logged in.
3. API access is disabled in TWS — enable File → Global Configuration → API → Settings → "Enable ActiveX and Socket Clients".
4. Wrong port — TWS defaults to 7496 (live) / 7497 (paper); IB Gateway to 4001 / 4002.

StreamXLS also shows #N/A deliberately: its Fail Loud principle means that when a value is no longer trustworthy (for example, the TWS connection dropped), the formula returns #N/A rather than a stale number. Start diagnosis with =RTD("Tws.Rtd",, "status", "IsConnected") — 1 means the TWS connection is up. Full walkthrough: IBKR RTD troubleshooting.