What should I do if I recently found out that my employer's worker comp insurance has been canceled for non payment. over a year ago?

I would consult with the human resources department at work as to why the worker's compensation policy of your employer is no longer in effect. Under state and federal law, worker's compensation is required to be in place. If the answer to your question is not satisfactory and there is no set date for installment of the policy, you should consult with a labor attorney or a representative with your local department of labor.