I have a pantry file that is stuck online. I can't remove it.
I was able to remove it. I created a Pantry List on my computer by the exact same name. The Sync screen showed to update to online. I then deleted the pantry list from my computer by viewing it in MasterCook on the computer and selecting Delete Pantry from the File menu. Now the Sync screen shows Remove to Online Account. I synced, and it removed it from online.
Note: This can happen if you use illegal characters in the file names. See this related article.