Short version: This message comes from Steam, not from Tradeit. Either your Steam account does not yet meet Steam's trading requirements, or Steam has put a temporary hold on your account after a recent Steam update or a sign in on a new device. Nothing is lost. Your items and balance stay safe in your Tradeit inventory, and a temporary hold clears on its own.
Why does it say "You are not able to receive trades"?
Steam blocks the trade offer before it reaches you. Tradeit cannot override a Steam restriction on your account. There are two common causes, and the checklist below tells you which one you have.
Check these four things on your Steam account
Your Steam Guard has been enabled for 15 consecutive days
Your Steam Mobile Authenticator has been enabled for 7 consecutive days
Your Steam account is higher than level 0
Your Steam inventory is set to public
If any of these do not apply to your account, that is your answer. The day counters run from the moment you enable each feature, so if you turned Steam Guard on recently you need to wait out the remaining days. If you have not set up the mobile authenticator yet, see How to enable the Steam Guard mobile authenticator? for the full setup steps.
Steam Guard is already on, so why am I still blocked?
Steam also applies a temporary hold after certain account events, even when Steam Guard and the mobile authenticator have been active for a long time. The two most common triggers are a Steam client update and signing in to your Steam account on a new device. Many users see this reported as "Code 15".
This is Steam's own security restriction. Tradeit cannot lift it, shorten it, or see how much time is left on it. It clears by itself once Steam's holding period ends, and you do not need to do anything to remove it.
While the hold is active, avoid signing in on more new devices, because each new sign in can start the holding period again. When the hold ends, open your trade or withdrawal on Tradeit again and it will go through normally.
Steam has been adding more trade security in general. If you want to understand the wider set of Steam trade rules, read What is Steam Trade Protection?
What happens to my items while I am blocked?
Nothing is lost. Items you bought or traded for stay in My Tradeit Inventory until Steam lets you receive trades again. You can withdraw them once the restriction is gone. For other reasons a withdrawal can be held up, see Why can't I withdraw an item?
What to do if everything checks out
If all four requirements above apply to your account, you have not signed in on a new device recently, and Steam still refuses the trade, contact our support team. Tell us your Steam account name and roughly when the error started, and we will look into it with you.