Banking questions

I tried to transfer money to my son’s college account and I typed the wrong expiration date for the credit card so it got rejected. Then I tried a different card and it said that date was bad too, but it was not. However these “bad” transactions showed up in my credit union account.

Why is this showing up in my credit union account if the transaction was rejected? I don’t understand how they can reject a transaction on the one hand, but yet put a hold on my money on the other hand.

Also why is it telling me the expiration date was wrong on the other card when it was correct?

I’d call customer service.