One of your company's applications stopped working after a network change window. The application relies on an on-premises database server (IP: 10.2.1.25) that is no longer receiving traffic. The only change implemented was the creation of three new VPC subnets: 10.1.0.0/16, 10.2.0.0/16, and 10.3.1.0/24. The on-premises router advertises the 10.0.0.0/8 network.

What is the most likely cause of this issue?