Exception "Configured unique ID is not present in SAML response"

I'm getting the following error when a successful authentication is passed back to the Drupal site:

Referrer	https://idpurl.com/idp/profile/SAML2/Redirect/SSO?execution=e1s1

Message	Exception encountered while processing SAML authentication response: Configured unique ID is not present in SAML response. in Drupal\samlauth\SamlService->acs() (line 185 of /drupal/web/modules/contrib/samlauth/src/SamlService.php).

I can decrypt the response XML using the SP's private key (tested on https://www.samltool.com/decrypt.php), but it doesn't look like the SAML module is decrypting the response.

The unique ID is present in the decrypted response, so that is why I am thinking that the module is not decrypting properly.

Any suggestions?