You have recently restarted the database service on an On-Premise server, and the Jive Webapp can no longer connect to the database. This used to work before the restart and you have not changed any configuration like database port or password.
SBS Logs show the below error message:
com.jivesoftware.base.database.ConnectionPool createConSEVERE: Failed to retrieve connection from DriverManager
java.sql.SQLException: Network error IOException: Connection refused (Connection refused)
This error means that the Webapp Node is having trouble communicating with the Database server. You should try restarting the servers that host both these services.
You may see the below error as well:
org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet [default] in context with path  threw exception [org.opensaml.ws.message.encoder.MessageEncodingException: Error creating output document] with root cause
java.io.IOException: Broken pipe
The above error does not hinder users from accessing the instance. It is likely due to a connection issue in your environment. Jive Support does not investigate issues that are not directly tied to unexpected functionality.
You can run the below command to check for deadlocks, if you suspect there is a deadlock to the database in one of your webservers:
$ grep "deadlock" <JIVE_HOME>/var/logs/sbs.log* | grep ERROR