Exam AWS Certified Solutions Architect - Professional topic 1 question 900 discussion

A company has implemented a new security requirement. According to the new requirement, the company must scan all traffic from corporate AWS instances in the company's VPC for violations of the company's security policies. As a result of these scans, the company can block access to and from specific IP addresses.
To meet the new requirement, the company deploys a set of Amazon EC2 instances in private subnets to serve as transparent proxies. The company installs approved proxy server software on these EC2 instances. The company modifies the route tables on all subnets to use the corresponding EC2 instances with proxy software as the default route. The company also creates security groups that are compliant with the security policies and assigns these security groups to the EC2 instances.
Despite these configurations, the traffic of the EC2 instances in their private subnets is not being properly forwarded to the internet.
What should a solutions architect do to resolve this issue?