Try this symbol: MNQ-FUT-202409-MNQ-CME-USD

I have some more symbols and some hints in this post: See Assets section in post

I used the IB TWS to try and fill out the Assets.csv file with the correct symbol data but I'm not positive the Assets setup for each symbol is correct but it seems like it is. I would enter the symbol in the Watch List in IB TWS and Right-click to get the Symbol Information. Futures symbols are always a royal pain to get right.