Random inability to access Salesforce

This can appear in the log files in different ways. Here are some possible causes:

1. Another instance of Sitecore, that is using expired credentials, is pointed at Salesforce. Sitecore partners need to be aware of any development websites that point to their customers Salesforce production instances. If partners run scheduled tasks, like analytics updates, with expired passwords, this will intermittently lockout the customers API user. You can discover this in the customer’s Salesforce API users login history which would show an IP address that belonged to the Sitecore partner.
2. The Partner API count could be running near its limit. If exceeded, it will close the API for 24 hours. Check the running tally in Salesforce.
3. You are running a server farm and not all servers are set up and licensed correctly.