The results of the Iowa caucuses were significantly delayed as "quality checks" were required because of inconsistencies in the voting data.
The Iowa Democratic party said results were not expected until "some time Tuesday – at least."
A new app for tabulating and reporting the caucus votes was introduced this year and while it was intended to make the voting process faster and easier, it has resulted in significant delays and complications.
"I have been on hold for over an hour with the Iowa Democratic party," Shawn Sebastian, an Iowa caucus official told CNN.
"The app by all accounts just like doesn't work, so we've been recommended to call into the hot line, and the hot line has not been responsive."
Several officials involved in the vote have reported issues with app. Des Moines county chair Tom Courtney said the app was "a mess".
Iowa's Democratic party officials are working through the night to ensure the accuracy of the results.
"We found inconsistencies in the reporting of three sets of results," Iowa democratic party communications director Mandy McClure said.
"In addition to the tech systems being used to tabulate results, we are also using photos of results and a paper trail to validate that all results match."
She said the app did not go down and was not hacked.
Joe Biden’s team released a statement condemning the “considerable flaws” in the Iowa caucus reporting system.
“The app that was intended to relay caucus results to the party failed,” it read.
All Democratic candidates said they won the caucus.
The presidential nomination race is highly contested, with four top candidates competing for votes at more than 1,700 polling stations in Iowa.
The front-runners in the race are Elizabeth Warren, Mr Biden, Bernie Sanders and Pete Buttigieg.
There are 41 state delegates up for grabs in Iowa, but a total of 1,991 delegates are needed to win the Democratic presidential nomination.
The next vote will take place in New Hampshire on February 11.
