@Sathish are you able to login to nexus with username/password?
https://app.camunda.com/nexus/
This dependency is available in path: https://app.camunda.com/nexus/repository/camunda-bpm-ee/org/camunda/bpm/springboot/camunda-bpm-spring-boot-starter-rest/7.13.0-ee/camunda-bpm-spring-boot-starter-rest-7.13.0-ee.jar
So in your pom.xml, add configure repository like this:
