The Electoral Office has apologised to people affected by mistakes made in the run up to last year's general election but "strongly refuted" alleged failings in its handling of the poll.
In December, it was reported that some people had lost their chance to vote because of issues with the Electoral Office.
It is understood some voters were given the wrong deadline for registration.
It is not clear how many voters were affected.
The Nolan Show, which broke the story in December, spoke to one woman on Tuesday who said she, her husband and her son were unable to vote because they were told the deadline to submit additional evidence for their registration was 26 November.
The actual deadline was 4 December.
In a statement, the Electoral Commission, which oversees the running of elections, said that in its "ongoing analysis" it had seen "no evidence of any systematic issues with the administration of this poll".
Virginia McVea, the chief electoral officer with the Electoral Office, said it had carried out a "thorough investigation into allegations that were made and we are satisfied that many of issues raised were inaccurate or unfounded".
"However, we have made it clear that give we dealt with hundreds of thousands of documents during this election in a very short period of time, mistakes are inevitable due to human error.
"We apologise to the people affected unreservedly."
She added that the office had provided a "full and detailed report to the secretary of state" and had updated local political parties.
Concerns were originally raised after the December 2019 vote by a whistleblower to the Nolan Show who worked in the Electoral Office in the run-up to the election.
He described the registration process as "chaos" and claimed that many people lost their chance to vote.
He said the office told people the deadline to submit additional evidence, such as proof of address, was 3 December.
However staff were allegedly aware the deadline was 4 December - which was subsequently extended to 5 December.
On the Nolan Show on Tuesday, a woman said she, along with her husband and her son, were unable to vote after attempting to register.
Elizabeth told the show that the office asked for additional evidence to support the application but told them the deadline was the 26 November, when the actual deadline was 4 December.
"I have always voted, because I want to have a say in how things are run in the country. I care about issues that affect me and my family and other people," she told the Nolan Show.
Elizabeth added she felt that right was taken away from her and she has lost confidence in the electoral process.
"Other people have a right to vote for people who represent them, represent their beliefs, what was important to them. We didn't get that opportunity this year, and that is quite sickening," she said.
"What are they going to do about it? Because at the moment it is just being brushed under the carpet as a typo. The most amazing typo in the world."