Hi Carlos,
> I've created 5 volume replications between 2 nodes of an HCI cluster.
Do you mean between two storage clusters in an HCI cluster? You can't replicate within one and the same NetApp HCI storage cluster; you can snapshot & clone volumes in the same cluster, but for replication - sync or async - you need 2 separate storage clusters.
If you have 1 cluster, then that can't be set up. Assuming you have 2 clusters, I think replication cannot start because of MTU or some other problem.
Can you try to create 2 junk vols (one 1GiB on one cluster, another 1GiB on another cluster) and see if those empty volumes can be replicated? If you have a network problem than that will likely fail as well.
You'd need MVIP to MVIP connectivity (so CL1NODES->CL2MVIP:443, and CL2NODES->CL1MVIP:443) and the same for SVIP (where MTU 9000 are used, unlike MVIP which can be smaller, like the standard MTU 1500).
Other than that possibility, are the both clusters the same major version of SolidFire (Element OS)?