What does the message "Your account has a minimum of 15 orders working on either the buy or sell side for this particular contract" mean?

When you see the message "No opening trades: ineligible PINK stock" it means an opening order for that contract is not allowed, even if your account has trading permissions for US Penny Stocks.

Additional Information…

You are attempting to add an order for a contract where an open order already exists on the opposite side of the market. Customers are prevented, by regulation, from entering a buy and a sell order for the same option contract. The right to be on both sides of the market is reserved for market makers…

The message refers to who cancelled the order. As an example, Cancelled by System is a message you will see when one OCA leg of an order is canceled by the User then the IBKR system will cancel the other leg of the OCA Group. The message for the first leg will be displayed as User Cancelled as the user acted to cancel the order.  The other OCA leg message will show Cancelled by System as the IBKR system was active in cancelling that order. An Invalid Order means the order was either created incorrectly and when submitted the IBKR system would not accept the order. Or the Invalid Order was created in a manner the exchange would not accept or a change occurred like the contract expired so the exchange could no longer hold the order…

It is against regulatory rules to trade with your own orders. If you currently have a limit order working and you place a MKT order for the same product on the other side of the market, you will receive this warning as it is possible those two orders could trade with one another. To avoid this, use limit orders with specified prices so your open Buy and Sell orders will not cross…