It's really difficult to say what the problem is, but I guess you are stopped-out (your positions are liquidated, mistakenly called by most traders 'Margin Call'). The Stop-out level at FXDD is 100%, not 5%, 25%, 70% etc. like with other brokers (Alpari, etc.)
To make sure if this is the reason, check the comments and you will have a message like this:
So don't place too big order sizes. The leverage is only 1:200, so can open max. 1.5 lots with 1k.