@CAMARAMAMY, Your data is likely inaccessible as your cluster is likely network-partitioned and the nodes are isolated (or at least one is) - there are basically 2 aspects (ignoring corner-cases for now) that govern vSAN nodes being able to communicate with one another:
1. They have a vsan-tagged vmk interface that can communicate with the other nodes vsan-tagged vmk interfaces, at the MTU these vmk have set (and assuming the remainder of the network stack end-to-end supports this) e.g. they are in the same VLAN and subnet and no required ports hindered (most important ones being UDP 12321 and TCP 2233).
2. All nodes have unicastagent entries informing them of the correct and current IPs and UUIDs to communicate with the other nodes.
All of the information that is required to troubleshoot and test all of the above (without vCenter available) can be retrieved via the following:
# esxcfg-nics -l
# esxcfg-vmknic -l
# esxcfg-vswitch -l
# esxcli vsan network list
# esxcli vsan cluster unicastagent list
# cmmds-tool find -t HOSTNAME
If unicastagent entries on any node are incomplete or incorrect these can be rectified using the above information (from each node) via the steps here:
https://kb.vmware.com/s/article/2150303
But before doing so, do of course validate there isn't some network communication issue between the configured IPs (e.g. no vmkping, MTU mismatch, no correctly tagged vmk etc.).
