Cat Brooks, 37, of Oakland, went to her polling location at True Vine Ministries at 896 Isabella St. in West Oakland and was told she wasn't on the list.
"I have been voting at this location for three years," Brooks said.
The poll worker recognized her from past elections, she said, and told her the mix up had been happening all morning.
The Alameda County Registrar of Voters, Dave Macdonald, however, said this is something that happens regularly.
"Every election we have a number of people voting provisional," Macdonald said.
Voters who are not on the roster of registered voters are given the option to vote provisional, Macdonald said. Provisional voters ballots are taken and the voter is verified.
"Almost all provisional ballots end up being counted," Macdonald said.
Brooks said she had heard from other voters at the polling location they also were not on the list, and forced to vote provisional.
A friend of Brooks, who is a poll worker at the East Oakland location at Melrose Elementary School at 1325 53rd Ave., said the same thing was happening there, according to Brooks.
Macdonald, however, said he hasn't heard a thing about any polling issues in Oakland, or throughout Alameda County.