Payne has not been feeling 100 per cent since her arrival in the UK, but the Melbourne Cup winner still hoped to take part in the popular event on Friday evening.
However, she was due to undertake a medical examination at the racecourse this morning and is not fit enough to ride.
In a statement released by Ascot, Payne said: "It is with great disappointment that because of a virus I have contracted since arriving in England, I find I am unable to ride in the Shergar Cup competition today.
"I saw the doctor yesterday and we had both hoped the medication prescribed would kick in, but unfortunately that has not been the case and I am not well enough to compete today.
"I had been looking forward to being part of this special event for a long time. Joining the girls team had been had been a major goal of mine over the last 12 months, since missing the opportunity due to injuries sustained in a fall last year.
"I would like to thank everyone for their support and encouragement and would love to return another time."
Nick Smith, Director of Racing & Communications at Ascot added: "It's such a shame for Michelle that she's unable to ride today. She's been looking forward to it all year.
"We hope she will be able to participate in the event another time and in the meantime hope that the British audience get to see her next week at Newbury, where she's due to ride Summer Mile second Kaspersky.
"We are very grateful to Hollie for stepping in."
Doyle has made great strides this season and as her only previously booked ride is at Lingfield's evening meeting, she will not miss any engagements.
Doyle will be allowed to claim her 3lb allowance.