Welcome to the Community,
please double check your DNS entries for the host and vCenter Server and make sure vCenter Server is able to resolve the host's short and FQDN names and vice versa. In addition to this also double check the network configuration on the ESXi host for e.g. typos in the DNS name etc.
André
PS: You are welcome to open a new discussion. You will usually get more responses than posting to an old, already answered discussion.