There is supposedly a site wide ticket open, but it may not be your specific issue since I cant know exactly what steps you are using. This thread provides a host of problems that are being reported and hopefully worked on actively.
Unable to edit the HTML section on listings - The eBay Community
Provide specific details or steps if you feel your issue isnt covered. Some posters are suggesting that contacting support to log support tickets is helpful even if a ticket exists.
Hope your issue is resolved soon.
