Not able run a process or run a task - option not available or disabled

Situation 

If you try to run a process and it seems that process is not available 

Example: 

You have been trying since the beginning of the week to load students for their timetable however the option is not available or is disabled, this means that someone has run the process already and it has not completed so you need to find the process and delete the task.

Solution 

Go to your Task (Bell) 

Verify in your Task queue if you have a task that is still “Processing” (Does not have a "Completed" task after the "Processing" task.) This is on a per user base.

Then, delete that first "Processing" task, as well all others that does not seem to have completed. 

This will give you the option to run the task (load students) now.