I agree with SGB, I'm afraid.
Everyone deals with grief differently and you can't make him grieve the way you think he should.
I truly understand how worried you are about him, and you have made it clear to him that you are there for him, if and when he wants to talk. But you also need to realise that he may not want to talk about it. He may simply not feel that he needs to talk about it.
My mum died 7 years ago, at the age of 66. She was ill with advanced breast cancer, so her prognosis was not great - I don't know how many years she would have had left with us - but she died very suddenly from an infection contracted when she was having chemotherapy.
So although we knew she was going to die, when she did, it was very sudden and unexpected.
We were very close - spoke every day on the phone, sometimes more than once.
I cried when we were in the hospital with her, and was a bit tearful in the days afterwards, but I never actually broke down in the way that other people did - or in the way that was evidently expected of me.
I never have done ever since, and I haven't experienced the overwhelming grief that other people talk about experiencing when they are bereaved. I found this very difficult, as I had expected to be totally devastated when she died, given how close we were.
So I went for some bereavement counselling. The most useful thing with this was when the counsellor asked me why I was there. I realised that actually what I needed was to be given permission to be the way I was - to not suffer overwhelming grief and to not break down in tears.
I have no idea why I reacted to losing my mum in this way. But it is very hurtful when people clearly think you are callous or 'wrong' if you aren't in a wailing heap. I know that members of my own family think I'm very cold. We went to visit relatives in Canada a couple of months after she died, and I kept being asked to talk about her. People would put on a specific tone of voice, with a sympathetic face, and come and put their arms around me, clearly giving me permission to (and obviously expecting me to) weep and wail. The more this happened, the more uncomfortable I felt - and it was actually very patronising and insulting). I couldn't 'perform' the way they were expecting me to. I was also very aware that they were judging me, and deciding that I couldn't have loved my mother very much if I didn't behave in this kind of way, which really hurt.
The counsellor's view of me was that I had actually been processing my bereavement in the years during her cancer, and that (especially as we had a very good relationship) had been able to come to terms with it in my own way.
You sound like you have a very good relationship with your DH, and so my best advice to you is to take your lead from him. Be kind to him, but let him do what seems right for him and please don't force him or push the issue.
I'm sorry for your loss.