Revert to your prior snapshot and attempt again.
Did you follow the steps in the installation GUI and created your VM snapshots on appliances and IaaS servers?
If so you can Revert to Snapshot on the VMs that require it. Again this depends on what has failed and where. It will tell you in the installation GUI what has failed and what VMs need reverting to snapshot. There is also the option of retrying the IaaS components if that is where it has failed without the need to revert to snapshot. Also don't forget to backup your IaaS SQL database.