Getting error as - "An error occurred while communicating with the partner site."

Summary: When creating a quote, we are getting this error as -

You have attempted an action that could not be completed. Please verify if the service is available, or contact your site administrator if this issue persists. Details: "An error occurred while communicating with the partner site."

Content (please ensure you mask any confidential information):

This issue is occurring only in our test instance, when comparing the configurations with prod, we dont see any difference. Please advice

Version (include the version you are using, if applicable):

25D

Code Snippet (add any code snippets that support your topic, if applicable):