SSISDB upgrade failed

After migrating SSISDB (2014) to new server (2016), upgrade of the SSISDB failed with the below error.  The migration of the db was performed following the instruction in the link below.  

Object reference not set to an instance of an object. (Microsoft.SqlServer.IntegrationServices.UITasks)

https://docs.microsoft.com/en-us/sql/integration-services/backup-restore-and-move-the-ssis-catalog?view=sql-server-2014