Problems arose in September when state regulators said they were closing the co-op and instructed policy holders to seek new insurance plans on the federal exchange. Initially, Health Republic plans were to stay in effect until the end of the year. But last week, the State Department of Financial Services said it had moved the date to Nov. 30.

The state said in a statement last week that a “review of Health Republic’s finances has found that the company’s financial condition is substantially worse than the company previously reported in its filings.” Consumers have until Nov. 15 to select a new plan under the federal health care law to avoid losing coverage in December.

Health Republic said it had operated transparently with regulators and had had an independent financial review in August. The company said in a statement last Wednesday that it was forced to shut down because it received less than 13 percent of the roughly $149 million that the federal government promised it under the health care law.

Sharon Schanzer, a self-employed graphic designer on the Upper West Side in Manhattan, said the experience with Health Republic had her feeling déjà vu.

Ms. Schanzer said she enrolled after having a similar policy with the Freelancers Union, a group that had been offering low-cost plans to independent workers. But in 2014, the Freelancers Union said it would cancel its plans for roughly 25,000 members, because the federal health care law had made it impossible to continue.

Ms. Schanzer said she opted for a $680-per-month plan from Health Republic. She found the plan affordable with her income, but it was more restrictive than the plan with Freelancers Union, which allowed her to see doctors outside the plan’s network. However, she said her opinion of Health Republic changed when she received a letter from the insurer saying it was seeking approval to raise her premium to about $850 per month.

The rate increase never came. Not long later, she received a notice that the company would shut down entirely.