SQL Server job stuck even after restart
Not using the GUID but using the T-SQL procedure: 

sp_stop_job 

Could help resolve issues like the one you are having.

Example:

exec msdb.dbo.sp_stop_job @job_name = 'enterjobnamehere'


Checking the current running queries for any queries started by the agent and killing these could also help.

An example of adapting the script to find running queries started by the agent service:

SELECT sqltext.TEXT,
req.session_id,
req.status,
req.command,
req.cpu_time,
req.total_elapsed_time
FROM sys.dm_exec_requests req
INNER JOIN sys.dm_exec_Sessions s
on req.session_id = s.session_id
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS sqltext
WHERE [Program_Name] like 'SQLAgent%';