Sunday was supposed to be the final deadline to enroll in health coverage for 2020 on HealthCare.gov, the federal marketplace for buying individual health insurance. But website glitches — that may have caused enrollment problems — prompted an outcry, and the government restarted enrollment Monday.

The new deadline is Wednesday, Dec. 18, at 3 a.m. ET. Consumers who already have an account can shop for plans and find out whether they qualify for subsidies to lower the costs of plans at HealthCare.gov. (Twelve states and the District of Columbia have their own health insurance exchanges — and their enrollment deadlines vary.)

The person who appears to have flagged the technical issue first was Joshua Peck. He worked on HealthCare.gov outreach at the Center for Medicare & Medicaid Services under President Barack Obama. In 2017, when the Trump administration slashed the outreach and advertising budget for HealthCare.gov, Peck founded the nonprofit Get America Covered to do some of that work outside the government.

"On Sunday, I received an alert that told me that there may be an issue on the site," Peck says. He went to the login page and got an error message. "It didn't tell people the system was having a problem; it didn't tell people to wait on the site and try again," he says. "It was incredibly confusing."

He shared the message on Twitter and called on CMS to extend the deadline.

That message was amplified by many high-profile Democrats, including presidential candidates Elizabeth Warren, Joe Biden and Pete Buttigieg.

Midday Monday, CMS Administrator Seema Verma seemed to have heeded the call.

CMS did not respond to NPR's request for details about the decision or for an estimate of how many people may have been affected by the website problems.

Charles Gaba, an analyst who tracks enrollment in Affordable Care Act exchanges, has a guess as to how many people may have had problems signing up on Sunday.

"I'd estimate that it'll be somewhere in the range of around 100,000 people," he says. He notes 36 hours is not a lot of time to let those people know they still have a chance to sign up for coverage in 2020. But "it's better than nothing," he says.

This is not the first time website troubles have kept people from signing up. HealthCare.gov had a famously rocky start in 2013. Even this year, the first day of open enrollment, Nov. 1, had problems. Peck estimated around 100,000 people may have missed out on coverage because of those issues.

Overall, enrollment seems to be down a bit from last year, a trend that has continued since 2016. President Trump has tried to change — critics would say undermine — the health exchanges in a variety of ways, but they have proved to be quite resilient.

Still, 27.5 million people are uninsured, according to the Census Bureau. A Kaiser Family Foundation analysis found that 4.7 million of them would be eligible for health care plans with zero dollar monthly premiums after subsidies.

The new deadline means a busy extra 36 hours for "navigators," who help people through the enrollment process free of charge.

Melanie Hall is a navigator and the executive director of the Family Health Care Foundation in the Tampa Bay area. She says the issues on Sunday didn't faze her — she just kept refreshing the page until she was able to get people enrolled. But she is glad there's another chance for consumers who might have been thrown off by the last-minute technical issues.

"For anybody that's calling in a panic today or tomorrow, we will have the availability to still make sure that they get enrolled if that's what they choose to do," Hall says.

She has already called back several panicked people to help them finish signing up.

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