Post vCenter upgrade to 8.0 U3 version vSphere Replication is in disconnected state.
VMware Site Recovery 8.8.x
VMware Live Recovery 9.x
vCenter 8.0 U3d has no version compatibility with vSphere Replication 8.8 and 9.0.0 hence sites was in disconnected state.
Post vSphere Replication upgrade to 9.0.2 issue was resolved and site got connected.
To confirm the Interoperability status, please refer Product Interoperability Matrix