That alert means that the process used for updating (VshieldUpdate) keeps working in the background, therefore everytime you try to update now, it reports that it is already running.
A way to solve it is to kill that process, so you don't need to reboot the machine.
Here are the steps for doing it:
- Open a terminal
- type top and press enter
- look for that particular process and write down its PID
- press q to close the top command output
- type the following: sudo kill -9 PID
note replace PID for the number written down previously
The next time you click in update now, the update task will start.
note: Although the post has already 6months, it is better to receive a late reply than ever...