Form failure: No message available

Hi Community, I’m new to Camunda and now i am using springboot application for deploying my programs but when i start a process then this error shown Form failure: No message available.
I am quite sure my html file works well and it locates in the path: main/resources/static and my bpmn file locates in the path main/resources. How can i solve that problem?


By the way, I just want to replace the form with the iframe in OSLC.html and localhost:8888 is the another web service that i design.