Here is the announcement by WST:

Allen Withdraws from Shenzhen Open

Mark Allen has pulled out of this month’s Shenzhen Open for personal reasons.
 
Allen was due to face Ben Mertens on Monday September 28th. Mertens will receive a bye to the last 32.
 
The event runs from September 28 to October 4.

Now this is becoming a bit puzzling, worrying even. Mark has not played competitively at all this season. “Personal reasons” could be anything really so we don’t know what is happening and, of course, we do not have a “right” to know. We can only hope that it’s not too bad. 😔