So you are at the point where you have HCX manager appliance deployed and you need to create a site pair with the HCX in the cloud but you keep timeing out or getting an error.
NOTE: This problem only occurs when you are connected to VMC with a Direct Connect over a Private VIF
If you use the Public URL such as https://hcx.sddc-13-52-170-232.vmwarevmc.com/ or the ip address you either get a timeout or Error that the SSL connection is untrusted
Step 1: Get the HCX Manager private IP in VMC. Login to the console and open your SDDC, click networking and security tab, on the left side go to gateway firewall and click to add new rule, then click Destination, then select System Defined Groups, Notice the HCX private IP.
Step 2: Go back to your on-prem HCX manager and ssh to the console
Edit the etc/hosts file and add the following line and save it
NOTE: It needs to be your private IP in VMC for the HCX manager and the Public URL