No. Insurers are required to investigate claims, but the fact that they start an investigation doesn't obligate them to pay a claim that they wouldn't otherwise pay. Once the facts are gathered and reviewed, the insurer can then make a coverage decision.
That said, if you feel your claim has been wrongly denied, is delayed, isn't fair, etc., our consumer advocacy staff may be able to help you. (We're the state agency that regulates insurance in Washington state.) Email us at AskMike@oic.wa.gov or call us at 1-800-562-6900.
Not in Washington state? Here's a handy map to help you contact your own state's insurance regulator.