Connectivity to this host is lost. You must map using at least one port on each controller that is physically connected to each host.

Hello, I think you can check a few steps below:

PowerVault ME5: Alert Message "Lost Connectivity to the Dell SupportAssist Backend" and Event Message "Scheduler: SupportAssist is Not Registered With the Dell Backend" | Dell US

PowerVault ME5: Failed to add initiators to the host | Dell US

Dell PowerVault ME5 Series Storage System Deployment Guide | Dell US

1. SupportAssist Connectivity: The PowerVault ME5 SupportAssist implementation requires a two-factor authentication to permit the initial key exchange between the PowerVault ME5 and Dell Secure Remote Servers. 
2. DNS Server Configuration: Ensure that both controller modules are configured to connect to a DNS server that can resolve *.EMC.com host names.
3. TCP Port Usage: For direct connections, SupportAssist on PowerVault ME5 uses outgoing TCP port 443 to either https://dell.to/3tPCopP or https://dell.to/3TXTeO6 hosts. If your organization uses SCG VE to proxy connections between the PowerVault ME5 and Dell Secure Remote Servers, the default port that is used is TCP 9443.
4. Adding Initiators to the Host: If you’re unable to map a new host initiator world-wide name (WWN) port to an existing mapped host using PowerVault Manager, you can use the PowerVault ME command-line interface (CLI) to add the initiator.