Start Job on Another Server Gives Error "Job Does not Exist"

This is MSSQL 2014
I have ServerA and ServerB. Each server has a linked server to the other.

I want to start a job on ServerB, from ServerA

On ServerA I run:
EXEC [ServerB\InstanceB].msdb.dbo.sp_start_job N'Job2';

It fails with error: "The specified @job_name ('Job2') does not exist"

This IS a named instance which makes the syntax a bit tricky. I have tweaked it every way, but it always fails. What am I missing?
Thanks, Jack

Almost certainly a permissions issue. The login used for the linked server does not have authority on the linked server to start a job.

Once again, ScottPletcher, you are exactly right. I checked ServerB and the login didn't have any roles. Took care of that and now my job on ServerA is able to start jobs on ServerB. Thanks for your help!