“A majority (59 percent) of the eligible but still uninsured say that they did not try to get health insurance from either their state marketplace, healthcare.gov, or their state Medicaid agency in 2014,” reported the foundation. “Many did not explore the new coverage options and financial assistance available under the ACA, perhaps reflecting a lack of awareness or perceptions about cost.”

A mistaken impression about the cost of coverage emerged as a large factor. Of those without coverage, 53 percent cited a perceived cost barrier as the main reason. These folks were eligible for the subsidy but simply thought the price tag would be too high for them.

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“Confusion about eligibility played a role,” Kaiser said. “Among the uninsured who were eligible, and who sought coverage, 37 percent say they were told they were ineligible for it. While it is possible that they were ineligible at the time they applied, it is likely that these people received incorrect information or misinterpreted information they were given.”

Turns out that the much-ballyhooed problems with insurance websites and hard-to-understand applications weren’t a huge factor.

“Only 20 percent of the remaining uninsured overall said they did not have coverage because they had an application still pending (12 percent) or because they didn’t finish the application (8 percent),” the foundation said.

But some of the 30 million uninsured really couldn’t get coverage. Kaiser found that millions in the states that hadn’t expanded Medicaid really didn’t qualify either for Medicaid or for marketplace subsidies.

“Many are low-income, including the nearly 4 million adults in the 'coverage gap' — those living in states that have not expanded Medicaid who earn too much to qualify for their state’s current Medicaid program but not enough to get ACA marketplace subsidies,” Kaiser reported. “Also ineligible for assistance under the law are millions of uninsured who have an offer of coverage through their employer that they do not take up, are undocumented immigrants, or have incomes above 400 percent of the poverty level and do not qualify for subsidies to make coverage more affordable.”