From what I understand this function being requested is a catalog lookup via individual ISBN from Ingram to your Vega catalog. In this case we have the following options.

In the configuration where you "Enter your library's Internet OPAC address" enter your preferred Vega Catalog URL.

In the ISBN specific search index enter either:

/search?query=

or our direct link to isbns:

/search/card?isbn=

The first option does a search for the ISBN in the everything search. Vega indexes ISBNs into the All/Everything search to help find individual titles by ISBN.

The second option is one of our 4 available options we added to use with 3rd party vendors to link directly to titles using IDs. These are all outlined here: https://documentation.iii.com/vega/admin/admin/LinkToWorksBook.htm

You will not be able to use the iMatch option in Ingram with Vega Discover as you did in Polaris because it uses z39.50 which is not supported in the Vega Discover catalog.

I've attached a small document provided to me by Suburban Library Cooperative with screenshots and extra info about the Ingram configuration.