Overview
eBay's Listing Policies govern how a listing itself must be written and presented - separate from how you conduct the sale afterward (that's covered in Selling Practices). These rules exist so buyers get an accurate, trustworthy view of what they're buying, and so search results stay useful.
What sellers should do
Write original descriptions and use your own photos, or eBay catalog images where offered
List only real, tangible items or services - no placeholders, "want ads," or blank listings
Use keywords that are actually relevant to the item
Give an accurate item location (city/state or city/country combination that makes sense)
Only offer one active fixed-price listing per identical item at a time
Follow the specific requirements for pre-sale items (e.g. upcoming phone or game releases) if applicable
What's not allowed
Copying descriptions or images from other listings without rights to use them
Stuffing titles/descriptions with unrelated popular keywords to manipulate search
Listing the same item more than once at the same time (duplicate listings)
Including links that send buyers off eBay
Adding JavaScript or other active content to a listing
Using third-party "trust" logos or endorsements to vouch for your reputation
Giving a false, vague, or misleading item location (e.g. mismatched city/country combinations)
What happens if a listing breaks these rules
eBay may hide or remove the listing, and will usually notify the seller by email explaining why. Repeated or serious violations can lead to warnings, activity restrictions, or account suspension. If a listing seems to have disappeared without any policy-violation email, it's more likely a search ranking issue than a removal - see eBay's Best Match guidance for that case.
Is this an eBay restriction or a 3Dsellers issue?
eBay-side: the listing was removed/hidden and the seller received (or can find, via eBay's Seller Help tool) a policy violation notice; the item simply isn't ranking well in search despite being live; a duplicate-listing notice from eBay.
3Dsellers-side: the listing looks fine and compliant on eBay itself, but 3Dsellers is displaying incorrect data (wrong price, category, images, or status) for it; an edit made in 3Dsellers isn't reflecting on the live eBay listing at all.
Tip for support: have the seller check the listing directly on eBay.com. If eBay itself shows a policy or compliance message on the item, this is an eBay Listing Policy matter and eBay's Seller Help tool is the right place to resolve it, not 3Dsellers.