A state Board of Elections spokesman says a check of 64,000 signatures didn't find enough registered voters. Those signatures were a sample of the more 330,000-plus submitted.
Gay marriage opponents want to ask voters in November if the state should amend its constitution to ban same-sex marriage.
Elections board spokesman Dan White says the requirement is that 95 percent of signatures be valid and they had 91 percent.
The measure can still make it to the ballot because supporters can appeal the findings of the board's review, which they plan to do.
The elections board meets Wednesday.