Symptoms

When opening the K2 process postal site, the production environment is pointing to the staging server.
 

Diagnoses

The client deleted his production site collection and restored the site collection in staging to the production environment. The connection string information (Among others...) gets stored in hidden lists on the site collection. This is the reason why all was pointing to the staging environment still.
 

Resolution

The easiest way to push environment settings to a site collection in this manner, is to activate the K2 for SharePoint components to the site collection again. We will pull the settings we need from SharePoint Central Administration and push then down to the site collection again.

Additional Information...
We keep a list of deployed processes, connections strings, process and action rights and some other settings in hidden lists on the SharePoint site collection.

By deleting the site collection and restoring one from a different environment, in essence you have wiped all the settings configured for that site collection and replaced it with settings from a different environment.

This might be okay if you had nothing running in production, but is not recommended when there are processes deployed and process instance running in the current environnment.