When should I attempt to build a bridge?

I’d say rebuild your relationship with your son first. You say “it seems he has left” as if you don’t actually know where he is living.
It’s still early days for Post Covid meet ups etc, so you need to take that into consideration too.
Hope it works out well for you all.

I think your instincts are right let your son sort his access before approaching her.

Was it you that contacted social services?

Sorry, I vaguely remember your posts and your concern seemed to be that your son didn’t get on with his adult step-son.

Why are social services involved with the baby?

I agree with 2020convert that it's your relationship with your son that is key to you seeing your GD keepingquiet.

Having unblocked your d.i.l. from your 'phone at least gives her a way of contacting you however, having been previously blocked by you, it seems unlikely that she'll do so.

I hope it works out for you too and would urge you to seek any contact with GD through your son and to avoid making contact with your d.i.l.

My son now has a flat a short walk away from his daughter. I feel relieved that he has space of his own and out of that toxic relationship, but that he's also close by so he can see his daughter often. I feel it is a move in the right direction, but in the past he's always gone back. I hope now he has his own place he won't need to.
I called SS several weeks ago more out of concern for DIL's fragile mental state than for the baby. They finally got to go to the house last week and things have moved quickly since then. I know they were told to take the baby to the GPs as she is very underweight. I haven't seen her for three months.
I presume the stepson is still in the house, but I really don't know and that isn't my business.
I will hold back from contacting DIL- I don't even know why I considered allowing her back in my head.
I think my son is free to ring and see me as he likes. I'm not well just now so I'm in no hurry to go there yet.
Thanks for your kind words.

It'll be up to social services on visiting rights for both you and your son, or if it's gone through the courts then it's the judge's decision.

Although visiting is encouraged, grandparents don't have the same rights as the parents. In some cases non-existant.

Grand parents have no rights at all. It's the children who have the right to know their extended family.

I wouldn't go to court on an issue like this. I came to terms that whilst he was with her there would be no place for me.
If he can make a go of making a stable life for himself then I should be able to see my son and his daughter together.
There is a possibility he will mess up and then I may never have contact with her unless DIL allows it- that is the reality I'm facing.
I will just have to see how it all pans out. I'm feeling more hopeful than I've been for some time.

I think you are doing the right thing by waiting until your son has contact with his daughter in place, and seeing her that way, rather than reaching out and going through your DIL.

I hope things get sorted out keepingquiet.

keepingquiet Hang on in there

I think the wise thing would be to wait for the SW involvement and investigation to come to some sort of a conclusion. If your son is willing to keep you in the loop about those, that would be good.

Update- conversations with son are regular, but short and he's not forthcoming with info. Today he said he was going to an anger management course. It is a week away from the first anniversary of his father's death. Whilst I feel anger management won't do him any harm (he has never demonstrated anger towards me or anyone who knows him) I have been on the receiving end of DIL's temper and it isn't nice and is the main reason I backed off.
Yesterday she posted on SM that she had incurred a fine for parking at hospital where she had taken baby. All she said was that baby was small, but when people asked about how baby was there was no response from her other than how furious she was at being fined.
I have rung social services four times this week and been promised call backs with no result.
So, going into another weekend without knowing what is going on.
Not much I can do though. Will attempt a meet-up with son next week or at weekend.
It's so difficult.

Perhaps you should leave the couple to sort things out. Ringing SS four times is way too much, they know you are concerned. You have no rights to see gc and it would be better if you build a supportive relationship with your son, it has to come from him, he knows you love him and there for him. He is doing all the right things by the sound of it. Your gd needs their father, that must come first. You Dil seems in fragile health and if you have blocked her and informed SS is unlikely to resume contact until she us able to manage her way.

I am leaving them to sort things out. Of course, these things take time. I think they are waiting for mediation, but all I get are mixed messages from my son. He is broken- but he still won't take any responsibility for what's happened. She won't even let him video call the baby.
SS didn't even know I was offering help, and said they always encourage wider family support- so I don't regret my persistence at all.
I am fully aware of my rights as a grandparent, which are nil. But this isn't about me, it is about the baby's needs.
My son is all over the place, he wants to support his child but she puts up barrier after barrier with no clear reason.
I'm beginning to feel DIL is much stronger both physically and mentally, than I was led to believe. She seems very happy and has begun posting pics on social media that I am not allowed to see, but my siblings are.
My granddaughter will be a year old soon and my siblings predicted that would happen, and she seems happy to get attention from them.
I am all over the place with this situation.
Do I ignore my granddaughter's first birthday? I was the only person (not even her parents) who bought her anything for Christmas.
I know my gifts will probably be rejected but I feel whatever I do will be used against me.
This is so incredibly difficult- I coped with cancer and losing two babies, but this is far worse. It is real, peristent heartache that I can never see being resolved.

I completely understand how you feel. Whoever said it was a living bereavement was right. I think just severing contact with grandchildren is wrong unless there is some abuse. It is cruel, not fair on the child or grandparent. What is so hard is knowing you can’t do anything about it, the instigator holds all the cards, you feel isolated and bereft. If you can, look after your own health and state of mind, be busy, get out and about, walk and join things, make a different life to the one you had. You have told them how much you love them, continue with cards and presents and hopefully, perhaps in a few months you can reach out again, hopefully things might be a little better and you will get a response. The longer it goes on the harder to reunite but it takes two. ?

Your priority is to take care of yourself. Go out, meet people . It must be so difficult for you and you are powerless to intervene. My heart goes out to you as you must be so worried. Please take care of yourself , you are important and being kind to yourself is essential. I hope you somehow find some peace.