The website wahealthplanfinder.org offers visitors a friendly, bright green welcome page, but the internal workings were plagued by glitches.
Still, some people were able to sign up for health insurance as part of the nation's new health care law, according to officials with the Washington Health Benefit Exchange.
Others encountered slow loading times and trouble completing online applications.
A call to a help line reached a friendly operator telling people the site was experiencing difficulties and to try back in an hour or so.
Richard Onizuka, CEO for the Washington Health Benefit Exchange, thanked people for their patience.
"While we have experienced some expected bumps in the road, the corrections made last night and continued enhancements to the site over time will ensure a smooth application process for those seeking and enrolling in health coverage," he wrote in a statement.
Problems closed the website on Tuesday shortly after it launched. The site reopened later in the day, but glitches continued.
Site managers blamed unexpected user activity and interaction with the marketplace for some of the problems.
Onizuka said his technical team did extensive testing before the launch.
In addition to the online marketplace, Washington residents can sign up by telephone or in person. Officials say it takes about an hour to go through the process for an individual and a little longer for a family.
Washington residents have six months to buy health insurance through the new exchange during the first enrollment period ending in March.
The state estimates about 1 million Washington state residents do not have health insurance, or about one in seven people.
The state hopes to enroll 130,000 people for health insurance in 2014 and another 280,000 in 2015. Another 325,000 people will be eligible to sign up for free insurance through Medicaid.
Under the Affordable Care Act, people who don't have insurance in 2014 will pay a fine when they file their federal income taxes in early 2015. The fines for people who ignore the new law are scheduled to increase over time.