West Brom have lost an appeal against the red card shown to Hal Robson-Kanu during Saturday's 1-0 victory at Burnley in the Premier League.
The forward was sent off late on following an aerial challenge with Burnley defender Matthew Lowton.
The Welsh international had earlier scored the goal that maintained the Baggies 100% start to the season.
He misses Tuesday's League Cup game at Accrington Stanley and Premier League games against Stoke City and Brighton.
Referee Martin Atkinson's original decision was upheld by an Football Association commission.