Can't get Amazon Lex Extended Slot to work with Regex pattern

Question

Trying to build a lex (Amazon LexV2) bot to look for account IDs that match our company's format. but having issues with the Slot.

I'm using an extended alphanumeric slot type (Slots>Built-In>Amazon.alphanumeric) so I can use regex to match the pattern for the account IDs. Every time I test it though, it just keeps repeating the Slot elicitation prompt.

All of my other slots work, just not this one. Is there a trick or something to getting extended alphanumeric slots to work?

 Regex
   Pattern: CP[0-9]{9}
   Example: CP123456789

Answer 1

I got clarification from someone at Amazon.

The regex pattern needed to be: [cC][pP][0-9]{9}