I don't have much experience with futures, but I was looking at CME's website on how much volume is traded with every expiration month, and it looks like there is no volume for ZN/SEP2020 and ZN/DEC2020. https://www.cmegroup.com/trading/interest-rates/us-treasury/10-year-us-treasury-note.html I tried to buy 1 contract ZN/DEC2020@ECBOT on my paper trading account at IB and nothing happened. Market order stayed in blue color (transmitted, not yet acknowledged). What is going on? I thought you can buy every expiration month available with high liquidity? I also tried to buy 1 ZN/JUN2020@ECBOT and this one was filled immediately!