Sign-up glitches marred the opening day of South Carolina’s one-year extension of free credit monitoring for 6.4 million taxpayers victimized in last year’s hacking attack on the state Department of Revenue.

The company running the effort said the problem will be fixed by Friday.

Joe Ross, president and founder of CSID, the Texas-based credit protection company hired by the state, said some people attempting to sign-on got an error message.

The problem occurred mainly because the identification information the people used to sign-in didn’t match the information South Carolina’s Revenue Department provided CSID, Ross said.

That happened for one of three main reasons, he said:

The person was not eligible.

The person improperly entered the information.

There were differences between the information the person used and what CSID had on file.

For example, people who moved might be rejected if the address they typed in didn’t match the one they used when they filed their taxes, or perhaps they used a nickname instead of full name.

The key information used to sign-in is the person’s name, address and the last four numbers of their Social Security number.

Ross estimated that 4 to 5 percent of those who signed on were rejected. That’s about 500 to 600 people.

Perhaps fueled by the outrage over the difficulties plaguing Obamacare’s online sign-up, some of those vented on Twitter and Facebook.

But CSID was prepared with a free call-in help service.

One person reported on Twitter that he was having trouble, but called the help line and “After 5 minutes on hold a nice woman enrolled me. Only took a few minutes.”

Ross said the average wait time for those calling in was about 7 minutes.

He said CSID is partly to blame for the problem because of the lack of clarity in the error notices people received when they were rejected. The messages did not specify what was wrong. “Our bad,” he said, and jokingly blamed the error on allowing his engineers to write the error message.

The problem would be fixed by Friday, he said.

Otherwise, he said, the roll-out went well. By early afternoon Thursday, he said, more then 12,000 adults, 700 children and 120 businesses had signed up.

He said CSID purposefully offered a long registration eligibility time, giving people up to 11 months to sign-up, so they don’t feel rushed.

CSID will unveil a public service ad campaign this week to fill people in on what CSID offers, why and how to sign up, he said.

Last October U.S. Secret Service agents notified South Carolina officials that a hacker had broken into the state Department of Revenue’s computers and stolen taxpayer financial identification information. The state soon learned that the hacker got the financial information, including Social Security numbers, of 6.4 million current and former taxpayers.

The state has since tightened computer security and offered free credit monitoring last year to those who were hacked. The state subsequently extended the monitoring for a second year, and offered CSID up to $8.5 million to do it, depending on how many people sign up.