1849424 - Error: "Could not execute dialog UserPasswords" when trying to log on to SUM

The following error is encountered when attempting to log on to SUM:

[Error ]: The following problem has occurred during step execution: com.sap.sdt.util.diag.DiagException:
Could not display dialog UserPasswords.
Could not execute dialog UserPasswords. See previous messages.
Error while trying to validate Administrator password.
     Possible reason: the J2EE engine is not started.
     Error while trying to get initial context.

Could not execute dialog UserPasswords, SUM, J2EE_Engine_HTTP_port, jndi_get_initial_context , Administrator, Could not display dialog UserPasswords, DiagException, Error while trying to validate Administrator password,  Error while trying to get initial context, the J2EE engine is not started , KBA , BC-UPG-TLS-TLJ , Upgrade tools for Java , Problem