You have set the slider to 50 EUR Margin.

50 EUR multiplied with OptF for BB Short USOil, plus a factor for previously skipped trades, results in 42 EUR. You need 125 to trade 1 lot, so the trade is not executed. The factor for skipped trades ensures that eventually one future USOil trade will be executed despite the too low margin.

The state of your other trades or your capital has no effect on the margin requirement for a trade.