When installing and configuring vCenter Operations Manager you receive the error message ‘Unable To Connect To vCenter Server. Details: Connecting to VC at https://vCenter/sdk failed’ when trying to enter the FQDN of you vCenter Server
Resolution
If you enter the IP Address of your vCenter then you are able to continue which means the issue is with DNS.
Go to your IP Pool > DNS and then enter the DNS Domain and an IPv4 DNS Server
Unfortunately, we now have to power the vCOPS vAPP off and power it back again for the new IP Pool settings to take effect. Once done, go back threw the initial configuration and you will be on the Import Data screen.
VMFocus 
it is failing with ip address too