Please first log out and quit the UI, then go to C:\Users\yourname\AppData\Roaming and delete the "iracing-electron" folder.

If you don’t see this folder, it may be because it is hidden. In the File Explorer window, click View and then check “Hidden Items”. See below for assistance.  

Another option to find the electron folder is to click into the My PC window and type %appdata% for the list to populate for the user logged into Windows. 

Once you have deleted the "iracing-electron" folder, log back into your iRacing account.