What if my vmProtect 8 virtual appliance fails

The backup archives are not tied to the appliance, so you can recover them from any computer that can see them. For example, if the server fails, you could repair the server, reinstall the appliance, and use that to access the recovery points. You could also install the vmProtect Windows agent onto a desktop/laptop and use that to either recover specific files/folders or even to restore entire VMs back to an ESXi server.

What you might want to test is that you (or the customer) are able to perform such a recovery.

Also, it might be a good idea to write up a simple contract that explains the backup system, the required maintenance (not details, just the main tasks such as rotating media and checking the logs, etc), and its importance, and then state that the customer understands the risks and is choosing to handle the maintenance themselves, and is forgoing a monitoring contract. For one, it gives the customer pause and might have them reconsider the monitoring contract. Secondly, if a catastrophy ever does occurr, the customer can't come back at you and say it's your fault because you told them the system didn't need any maintenance and would take care of itself.

Another option might be to have the customer agree to something like 1 month of monitoring just so you can ensure the backups are working correctly. That benefits both you and the customer because it puts some money in your pocket and gives the customer peace of mind that their backups are working correctly.