The state's Division of Insurance announced last week the co-op doesn't have enough money to operate beyond the end of the year.
That decision prompted the co-op to file a lawsuit asking a court for a temporary restraining order and injunction to allow it to sell new policies on the state health insurance exchange beginning next month.
After a two-hour closed door hearing Monday, the judge ruled against the request.
CEO Julia Hutchins said earlier the co-op had an investor who was prepared to put in $40 million and wanted the Division of Insurance to give it more time to show its financial solvency.
Colorado HealthOP has about 80,000 customers who will now have to find another insurer.
Open enrollment starts Nov. 1.