Help us to find the root cause
If you are on JIRA 7.x and connector version 6.0.11 and onwards, you may enable a DEBUG logging to help us identify what has exactly broken, the next time this problem happens:
Go to Cog Icon >System.
Under Troubleshooting and Support in the sidebar, click Logging and profiling.
Under Default Loggers section, click Configure logging level for another package.
Enter package name as net.customware.plugins.connector.salesforce.soap, with logging level as DEBUG.
If the problem happens again, please gather your atlassian-jira.log files and send to us at email@example.com.