The state had notified the Omaha-based company last November that unease about the accuracy of the voting machines may force a decertification of the units.
In a letter sent to the manufacturer, Assistant Secretary of State for Elections Bradley Clark cited a problem encountered during a Nov. 8 test of the system, when a vote was apparently displayed inaccurately.
The state's certification proc-ess requires testing of voting system vendors.
ES&S has been working with the state to address issues that were raised by the test, said a spokeswoman for Secretary of State Bruce McPherson.
"At this point, they've been very responsive to our needs," the spokeswoman said.
She said that shortly after the letter was sent, ES&S officials "came in and addressed each issue point by point. Each one has either been resolved or they will be required to find a solution."
She was unsure when ES&S will complete the compliance process.
An ES&S spokesman said the error was caused by a tester using her fingernail instead of her fingertip on the touch screen to cast a vote. The firm's iVotronic machines require that the fingertip be used, he said. The spokesman also noted that voters can review ballots before they are submitted.
The letter to ES&S also cited the tester's inability to see all of the choices on a single screen.
The spokesman said that the tester accessed the screen that summarized the number of votes cast and that the system does allow the viewing of all choices on a single screen.