Acronis Disaster Recovery Cloud: registering Disaster Recovery VPN Appliance fails with "Got unexpected response code [404]"

Symptoms

You are trying to register a newly deployed Disaster Recovery VPN Appliance and get this error message:

[The command fas failed. HTTP 404: Got unexpected response code [404] from ADRC service at [https://us-cloud.acronis.com/api/dr/v1/vpn/aapliance].]