"Connecting to Integration Service failed..." SQL Server 2016
Solved.

I was using SSMS 17.1 against SQL Server 2016.

SSMS 17 works great w SQL Server 2016.... except it cannot connect to SQL 2016 SSIS. To connect to SQL 2016 SSIS, you must use SSMS 16.x

Installed SSMS 2016, (v16.x), and it connects fine to Integration Services.