It's definitely not as colinsunderland said .It happened with me. One day I made a withdrawal before bed time, it was approved, went happily to bed, got up in the morning, when I logged in, I saw the money was back to my casino account. That was a few years ago when the withdrawal with visa took around 24 hours to reach my bank account, nowadays, the payment processor are using visa direct. What is happening with banks normally is any inwards payment is blocked and it went straight back to the sender, so I don't see why it cannot happen on same day.
I'm not saying I'm 100% sure "bank reject" is the cause, there could be another issue, that's why I said it is a good idea to talk to the bank to see if that is the cause.
I've had no issues with two other casinos I was lucky with ! Neither one and that was last weekend and the weekend before !!!
This is pure weird