HCW8078 – Migration Endpoint could not be created.

I trying to decommissioned the exchange 2010 and add exchange 2016 and run the HCW and got below error? all mailboxex are in O365 and need this smtp relay and management. 

I have f5 in front of old exchange server. do i have to add new server to to pool and re run?

Microsoft.Exchange.Migration.MigrationServerConnectionFailedException The connection to the server ‘webmail.domain.com’ could not be completed. Microsoft.Exchange.MailboxReplicationService.MRSRemoteTransientException The call to ‘https://webmail.domain.com/EWS/mrsproxy.svc’ failed because no service was listening on the specified endpoint

Notice this change the o365 send and received connectors and way to find the old settings?