Ask HN: Difficulty taking charge as PM

I am the PM on the client side of a major project that is using an implementation partner who is doing much of the analysis, design and config. They also have their PM who acts as lead PM. On our side, the business team has been working together for years, is experienced and is working very tightly with the implementation team. I am also new to the business domain. In short, I'm having trouble getting on top of things as PM and feel like I am chasing after the rest of the team. I don't feel like I'm adding enough value. Has anyone been through this?