Can someone help me find put why it is i cant open the game? When i am clicking to open it it comes up with a box saying 'only a single instance of this application can run' i dont have it open already.

Try the launcher repair utility initially - link

 

If it persists make a new thread in that forum - Link

 

Edit - with the launcher closed also delete any patch folders if they exist

Edited December 26, 2016 by OwenBrooks

You quit the game, or it crashed, or whatever, and didn't exit properly, so the swtor.exe is still running in the background.

 

Open the Task Manager. (Hit CTRL+ALT+DELETE then click on Task Manager). On the Processes tab, right-click on any SWTOR process(es) in the list, and then click End Task.

Run the Launcher again.

Adric_the_Red

 

This issue can occur without even having run the launcher previously, but if ending the processes help that will be great, but this is an issue I haven't seen for a while now , however in the past the repair utility is the best thing to try initially

 

Example thread - link