Upfront CSS Editor appears broken


The Upfront CSS editor seems to have broken as it will no longer load any code into the editor window and the editor window itself seems to have an irregularity in the top border.

I have granted support access to the site.

Prior to the failure of the editor I was working on custom css for the popup pro plugin. Deactivating the Popup Pro plugin made no difference to the problem.

I have deleted and reinstalled the Scribe theme and cleared caches but the editor is still not working.

Any suggestions as to how to resolve this issue?