Hi,
Once you're on the HikaShop configuration page, go under the Advanced tab and there you have the "Editor" setting.
I suppose you had JCE selected in there on the old website. And thus, in the database, JCE was still there.
Since JCE is not available on the new website, the "Editor" setting of the HikaShop configuration doesn't have that option. And thus, once you save the HikaShop configuration once, it will use the new default value of that setting and it will automatically fix the problem since it then won't look for JCE anymore.