Need a bit more background info here. Is this a new VCHA deployment that isn't working, or one that has worked before, but is now failing?

Are you deploying this on the same host or different hosts?

Are you using a dedicated Port Group for the Heartbeat network?

From the description, it sounds like you're deploying the Active, Passive and Witness nodes across multiple hosts, and they can't then talk to each other across those hosts due to lack of connectivity over the heartbeat network. Focus on this area. Simplify your deployment by deploying the VCHA nodes on a single host. Make sure the Port Group selected for the Heartbeat network is the same for each Active/Passive/Witness nodes, and double check IP addresses and subnet masks are correctly configured (you don't need a default gateway as you aren't traversing subnets). 

Let us know how you get on!