Rivals in the ruling movement led by Mahmoud Abbas, the Palestinian president, had at first presented two candidate lists, then decided that they wanted to merge them into one as a way to counter a challenge from surging Islamist rival Hamas.
Monday's ruling of the electoral court was needed because the official deadline for registering candidates was 14 December.
After an appeal, the court said it would reopen registration for a further six hours. It was not immediately clear when the six hours would begin.
The justification was that operations were suspended for six hours by the elections commission during the registration process to protest against attacks by armed men on its offices. The attackers were from Fatah.
There are no differences between Fatah's factions on the political programme of negotiating for a state alongside Israel.
Younger members seeking a bigger share of power are challenging a corruption-tainted old guard.
Hamas, committed to destroying Israel, has been boosted ahead of the election by the division in Fatah - one of the gravest crises in its 40-year history.
Polls show that Fatah might get more than 45% if it united but could fall to 21% if it remained split.
Hamas, running for the first time in the legislative elections, gets about 30% in opinion polls. But it swept local council votes in West Bank cities last week, alarming Fatah as well as Israel.