FC Porto have demanded Sunday's home league draw against Arouca be annulled after the referee used a mobile phone to check a potential penalty.
With Arauca leading 1-0 after 90 minutes played, referee Miguel Nogueira awarded hosts Porto a spot kick that needed VAR review. Nogueira was called over to the pitch-side monitor, but was unable to communicate with the VAR hub.
After a lengthy delay, Nogueira was handed a mobile phone to address the action with VAR officials. Despite being unable to see any images in the monitor, Nogueira overturned his initial decision and no penalty was given.
The Refereeing Council of Portugal's Football Federation said that the VAR delay was caused by a power failure at Porto's Dragao Stadium, which the club has vehemently denied.
The Portuguese giants claim it was a human error by VAR technicians, who failed to connect the cable from the stadium's power source to the VAR equipment.
"This fact was acknowledged by the Altice technicians themselves when they replaced the equipment, which was then supported by the stadium's power," a statement said.
Porto have asked the Portuguese league for Sunday's result to be cancelled due to "a misconduct by the refereeing team."
"Nogueira's action constitutes a violation of the rules of the game and an error of law with a potential serious impact on the outcome of the match," a club statement said.
The game ended 1-1 with Evanilson finding a last-gasp equaliser after three minutes earlier Porto's Wenderson Galeno had his penalty kick saved.