This error occurs due to eBay restrictions concerning multinational options. The length of associated option title must be less than 50 characters. This is true for Configurable, Grouped, Bundle, and Simple product with Custom options.
Please note that only first 30 characters will be seen to the buyers looking for your items. Thus, if you need your customers see the entire title, the length of 30 characters or less is required. Anyhow, if the title of 50 characters or less is provided, the product with variations will be listed on eBay successfully.