Few people know that it is possible to file a complaint for an unjustified non-renewal: Getting Help | CA Department of Insurance. An example of when a non-renewal may not be justified is if you recently implemented mitigation measures at the request of your insurer. The complaint form can be downloaded here: CA Dept of Insurance Request for Assistance (RFA non-health) [PDF]
Some have reported success with this tactic. A recent (2024) example was posted on NextDoor here (this link may not be available to all): (14) Just wanted to share that we received a notice of non-renewal on our home owners insurance and were able to RESOLVE it by filing a complaint with the Department of Insurance. — Nextdoor