There is no solution. Your bank or other business is forbidding the messages from being sent. Google has no control over it.
Details: "Shortcodes" are not ordinary SMS messages coming from a regular 10-digit phone number. Instead, they are sent by third-party service providers, using a five or six-digit number. Normally, this would not be a problem for Google Voice. However, Google Voice numbers are not true mobile phone numbers; they are fixed-VoIP landline numbers with text messaging spliced on, via a third-party system.
The bank's fraud prevention policy only allows these messages to be sent to true mobile numbers. This is because it is relatively easy to hack the SMS system and the hackers are often in other countries, using VoIP phone numbers.
So: it's an anti-fraud measure, and the bank won't make any exceptions. You must use an ordinary mobile phone for these shortcodes.