Strategies/Playbooks around Disengaged/lagging clients during implementations

Hello, Amazing community members!

I'm reaching out to understand and come up with creative ways to push lagging/disengaged customers resulting in delayed implementations. We have mapped CS counterparts at CSM, VP, and CEO levels. Even with exec sponsorship + Clear action items for clients, the resources assigned don't move the needle. How have you navigated through this challenge? 

Thank you very much in advance!
Yash