Ally
Was this a new claim for ESA?
There is a tick box on the ESA1, which you complete when you initially make a claim, saying that you only want to claim Contribution Based ESA, did you tick this? If you did then they will only assess you for ESA(CB) and if you have no NI Contributions which your post suggests, then your claim would be rejected.
If you did not tick the box then you should contact the DWP to ask what is going on as whilst they will still check your eligibility for ESA(CB) they should also check it for Income Related ESA.
I assume that you believe you would be eligible for ESA(IR).
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems