Connecticut seemed to be a bright spot. Access Health CT sent out a tweet shortly before noon Tuesday, confirming the marketplace logged 10,000 visitors in the first three hours of operation and 22 enrollments.
California, home to 15 percent of the nation's uninsured, reported delays online and on the phone because of heavy volume.
In Portsmouth, N.H., Deborah Lielasus tried to sign up for coverage but got only as far as creating an account before the website stopped working. She said she expected problems.
Lielasus, a 54-year-old self-employed grant writer, currently spends about $8,500 a year in premiums and more than $10,000 for out-of-pocket expenses because she has a health condition and her only option has been a state high-risk insurance pool. She said she expects those costs to decrease significantly.
As excited as she was to sign up, she said, her anticipation was tempered by dismay over the government shutdown that was led by congressional Republicans who want to block the health insurance reforms.
"I'm really happy that this is happening, that this is being launched ... I feel like it's a child caught in the middle of a really bad divorce," Lielasus said.
The shutdown will have no immediate effect on the insurance marketplaces, which are the backbone of the law, because they operate with money that isn't subject to the annual budget wrangling in Washington.
The Obama administration hopes to sign up 7 million people during the first year and aims to eventually sign up at least half of the nearly 50 million uninsured Americans through an expansion of Medicaid or government-subsidized plans.
Many states predicted that an initial surge of interest would test the online system, but they expect most people to sign up closer to Dec. 15, which is the deadline for coverage to start Jan. 1. Customers have until the end of March to sign up in order to avoid tax penalties.
Under the law, health insurance companies can no longer deny coverage to someone with a pre-existing medical condition and cannot impose lifetime caps on coverage. They also must cover a list of essential services, ranging from mental health treatment to maternity care.