A link for Taobao, 1688 or Weidian could not be working for three reasons: it could be mistyped, the item could really be dead or you need to login.
First you should check for a invalid link. Try the universal link converter, it should turn red if the link is invalid. An alternative is also putting the link into google. If you get results it's most likely a valid link and the item has just been removed recently.
If the link is dead because the item has been removed, there's nothing you can do, except doing some research to see if the seller has opened a new store.
If you get redirected to a login page, you should login first. If you don't have an account yet, try to make one. If you insist to find out if the link works before you go through the trouble, try to google it and see if there are recent posts. You can also google the id part of the URL.
added: 10/16/2023 , modified: 10/16/2023