you might have encountered "pacing violation". "We allow 60 backfill requests within a 5 minute period. In the past, once you exceeded that limit we queued up additional request but delayed data to maintain a ratio of 60 per 5 minute period. Keeping the additional request in a queue and delayed, caused stress on our system. Request that exceed the limit will now be rejected."
My ES was ok but not my DAX and ESTX%) indices. It might be a quote limit. I have four option chains with two months displayed.
If I may ask, how do you make 60 backfill requests in a 5 minute period? That seems like it would be difficult, unless I'm misunderstanding. OldTrader