This looks like slow response from from Vcenter Server and hence the time-out. You can increase the Timeout to greater than 600 sec ( default) but before that you do the following.
1. Check you have provided the correct IP, Port etc.
2. From your WFA server, Open VMware PowerCLI console and connect to your VC using the following command:
Connect-VIServer -Server <VC_Hostname_or_IP> -User <user> -Password <password>
3. Command : Get-VM
to list out the available VMs.
If all this finish in decent quick time, increase the timeout of Datasource to larger value like 1000 sec and try again.
If this post resolved your issue, help others by selecting ACCEPT AS SOLUTION or adding a KUDO.