Don't know if the user would able to know the reason why his withdrawal got cancelled. But I think the best approach here is to let him know that he can contact you thru pm then discuss those issues he encounter, then you are the one who will come with your technical team to solve his issue.

Anyways the people who claim that he's withdrawal cancelled didn't post anything to update his case so maybe we cannot assume that his issue is true or not.

For the mean time maybe focus to apply those suggestions given by people since somehow this is for betterment of your casino.