A consultant sot up and successfully tested an integration between the source system and a...

When the consultant encounters API call limit errors after switching the integration from a sandbox to a production environment, the likely explanation is:

Different API Call Limits for Sandbox and Production Environments:

Salesforce environments have different API call limits based on the type of environment and the organization's Salesforce edition. Sandbox environments often have higher API call limits for testing purposes, while production environments have stricter limits to ensure performance and reliability.