Dilemma with kids father

Hey everyone, I’m in a dilemma regarding my kids father.

Long story short, we have joint custody as of December 2023. My kids live with me now and we have the standard parenting plan in place. My ex is a class A narcissist so I assume most of you know what I dealt with and what they dealt with while they lived with him. Since they have been with me he has not even reached out once regarding the kids and has ignored my messages about them calling him or seeing him… it’s been 2 months now and he’s MIA.
My heart breaks for my kids because I want so badly for them to have a relationship with their dad, but it’s like he just abandoned them. Should I stop trying to reach out to him regarding the boys? I just hate seeing their faces when he doesn’t respond back.
I’m at a loss on what to do. I so badly want to have a good co parenting relationship for our kids sake and want them to have a relationship with their dad, but I know I’m dealing with a Narcissist so it’s only when it’s convenient for him.
Please give me advice/ personal experience or anything that I can do to help my kids cope with this situation.