too_many_requests

All concurrent market-data request slots for this account are in use.

HTTP 429.

Likely cause: Too many parallel history or market-data calls.

What to do: Wait for Retry-After, or send fewer calls at once.

Retry: Yes. Nothing happened (or it was a read), so repeat it, after Retry-After when present.

Listed under Market data and platform support in Errors. Send the error’s requestId to support and we can find the request.