Problems with the federal health insurance website have prevented tens of thousands of low-income people from signing up for Medicaid even though they are eligible, federal and state officials say, undermining one of the chief goals of the 2010 health care law.

The website, HealthCare.gov, is primarily seen as a place to buy private insurance with federal subsidies, but it is also a gateway to Medicaid, which generally provides more benefits at less cost to consumers. …

The Obama administration has adopted what it calls a “no wrong door” policy: If a person files an application with the exchange for private insurance but appears to be eligible for Medicaid, the exchange will automatically transfer the full application to the state Medicaid agency, and vice versa.

“We have not seen much progress on the flow of data from the federal marketplace to the state,” said Monica H. Coury, assistant director of the Medicaid program in Arizona. “After a person is assessed as potentially eligible for Medicaid, the application just sits there in the federal marketplace. If you need insurance because you have a serious medical condition, that delay could be harmful.”