For Java version 7.0 and above
1) Navigate to the APM Insight Java agent folder
2) Each application/instance will have a separate folder. Remove the folder with the name `<application_name>_<application_port>`
3) Delete the `APM_Java_Instances` folder
4) Restart the application server
For Java version below 7.0
APM Insight agent state is maintained in the `apminsight.info` file (located in the directory where the agent jar resides).
Delete this file and restart the application. This will add the APM instance successfully.