You don't understand how banking works. Your bank holds the money when a transaction begins. If the transaction fails, your bank returns they money they're holding to your account.

As for why the transaction failed Valve probably doesn't have much information. You're better off asking your bank. All Steam Support can probably tell you is try again or try a different FOP. They can't force your bank to give them money from your account.

Trying more than once isn't a problem, lots of reasons a transaction could fail. Not trying again/trying later gets you what exactly? Potentially a lot of work for no reason if a second attempt succeeds. If it fails you've lost nothing.

Try it in the client, try it on mobile, try it in your web browser. Perfectly valid troubleshooting. That may mean several attempts.

thanks for the feedback!