“People have been lining up to vote since 5 a.m., but polling didn't start until after 10 a.m because the voting machines were down," Patrick Abeli, a voter in the eastern city of Goma told RFI by phone.
Voting officially began at 5:00 (0400 UT/GMT), but several machine breakdowns in the Kinshasa capital, Goma and Bukavu, brought voting to a halt.
In other places, some voters complained they could not find their names on the voters' list.
"Some people had to travel 25 km just to go and vote because their name had been transferred to another polling station without warning," explains Elvis Katsana, a blogger in Goma.
For those who were correctly registered, the other challenge came from the new electronic system, criticised by the opposition as vulnerable to fraud. "Some people don't even know how to use them," Katsana told RFI.
"I searched for my name for more than half an hour," one female voter in Lubumbashi, Congo's second largest city, told RFI's Service Afrique. "And even to access the voters' list, we were told to wait."
In the capital, electoral officials were still adjusting voting machines in one polling station, and in another, a technician was needed to restart equipment that had broken down, witnesses reported.
Despite the problems, long queues formed outside many polling stations. In Kinshasa, where torrential rain forced several voting centers to shut, the bad weather did little to dampen the hopes of voters, many of them women, young people and the elderly.
"I'm excited to vote, to be able to choose at last," one 18-year-old student named Rachel told AFP.
Three men dominate the field of 21 candidates vying to become next president of the Democratic Republic of Congo, Africa's second-largest nation.
Emmanuel Ramazani Shadary is a hardline former interior minister under EU sanctions and, according to some analysts, a likely puppet of President Joseph Kabila, if he wins Sunday's election.
His nearest challenger is Martin Fayulu, an outsider who shot to front-rank status in the final weeks before the elections, and Felix Tshisekedi, head of veteran opposition party, the UDPS.
Kabila voted early in the morning in Kinshasa at the same school as his faithful supporter Shadary, whom the latest opinion polls showed trailing Fayulu and Tshisekedi.
“My only concern is that we have this very heavy rain and probably voter turnout might be low, but hopefully the skies will clear, and the voters will turn out in numbers,” Kabila told reporters.
Symbolic voting in Beni
Voter enthusiasm was high especially in Beni, one of three opposition strongholds where the government cancelled the vote, citing health risks from an ongoing Ebola outbreak and ethnic violence.
Despite the cancellation, thousands of residents organised a parallel vote, which they have asked the electoral commission to take into account.
"People are voting in their manner. In Beni, the youth are determined to make their voice heard," Esperance Kazi, a resident in the North Kivu province told RFI.
"We are here to show the electoral commission and the authorities that Ebola was not the real reason to exclude us from this poll," she added, insisting that appropriate hygiene measures had been taken to prevent the virus from spreading.
Back in Goma, where the weather was clear, blogger Elvis Katsana reflects on the importance of Sunday's long-delayed vote: "We have been waiting for this since 2016," he comments.
"They are important because they are an opportunity for change," says Katsana, referring also to voting for the national and provincial assemblies.
Although Congo boasts gold, uranium, cobalt and other riches, little of that wealth filters down to the poor.
"This is a chance to reduce the rate of poverty, create jobs, (...) we have waited so long," said Katsana.
The last polls close at 17:00, although voting will continue for those still in line.