Southampton FC has promised vowed to refund all general admission ticket holders after hundreds of fans were left queuing outside St Mary's Stadium.
Fans complained at missing up to 30 minutes of the first home game of the Premier League season at St Mary's - the first with a full crowd after Covid restrictions were lifted.
The club said a new system to scan tickets took "significantly longer" than in testing.
It has apologised to all fans affected.
The Premier League against Manchester United tie on Sunday was the first competitive match played at the stadium since lockdown restrictions on crowd numbers were lifted.