That is called the launcher.
@ZOS_BillE tends to be the person who replies to threads like this so tagging him in case it speeds up the process.
I assume you have found the executable so you can start the game without using the launcher. Many have shortcuts on their desktop just for that and use the launcher only do download updates.
For your issue though I would suggest restarting the PC to see if that rectifies it. Repair probably only repairs the client but it is worth trying to see if it will repair the launcher. Beyond that there is probably a file that if deleted it will download the launcher again but I would wait for BillE to reply before deleting anything.
Tech support ticket may be faster than Bille as it is the weekend.