Hi Patel
I would phone up DWP to see what is happening, if you sent your form of by recorded delivery and you have proof that it was delivered then contact DWP, give them your RD ref number.
At this moment in time things are a bit hectic and errors are made but for peace of mind contact DWP, best time is first thing in the morning or in the evening.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems