If your account has been restricted in any way, you should be seeing a notification in your Account tab.
Possible restrictions include:
- Not having a verified e-mail address (click the button to receive an e-mail confirmation)
- Not having a verified Steam account (click the button to start the verification process)
- KYC limits
- Antifraud restrictions
If you need additional information about this or don't know what to do, you can contact Support.