This is the announcement on WST site:
Mark Allen has withdrawn from the Cazoo Champion of Champions due to personal reasons.
Ding Junhui has been invited to the tournament as the third player to earn his place from the WST World Rankings, following Ronnie O’Sullivan and Stephen Maguire.
The final place in the event will be taken up by the winner of the BetVictor English Open.
The draw for the 2021 Cazoo Champion of Champions will take place this Monday, 8 November.
Mark Allen is the defending champion…
He put this on twitter
Ronie has been invited on rankings but is still in the English Open draw, so he could still qualify on merit
Going by the Champion of Champions twitter account, Ronnie seems to have accepted the invitation
Ronnie O'Sullivan 