Why Can't I Join a Trade?

The reason you can’t join a trade will generally be that you already have an active trade and haven’t yet set your API Key. Without an API Key, you are restricted to making just one skin deposit at a time, and you may only join one trade at a time from a user without an API Key. If the trade was listed by a user that does have an API Key, you may join multiple of these trades at a time.

Setting an API Key will ensure that your deposit has been recorded, which will make it easy to view every skin you have deposited and track which user has it. This will make it easier to join multiple trades should you choose to do so, without worrying about having any duplicate or invalid messages.

Once you set your API Key, these restrictions will all be lifted. You’ll be able to deposit and withdraw freely, allowing you to create and join as many trades at a time as you like, without seeing the invalid message.