Open Question: What can I do if 2 insurance companies each say the other is responsible to pay my claim so they both deny it?

I live in California, btw. So what happened is that I was taken off work due to extreme stress. There was no doubt that I really needed time off and was having a lot of physical and emotional symptoms due to the stress. It was mostly work-related, and I was taken off for almost three months. Even the man who interviewed me from the worker's comp insurance company agreed that the conditions