In order to be able to trade with non-friends (other DMarket users or bots), you need to set your inventory settings to “Public”.
To do this, please follow these steps:
- Go to your Steam profile
- Click “Inventory”
- Find “...” next to “Trade Offers”. In the drop-down menu click “Inventory Privacy Settings”.
- Set “Inventory” to “Public”.
Done! Your inventory privacy settings now meet the requirements.
Important: after changing your Steam inventory to "Public", you may need to wait up to 20 hours for your Steam inventory to be properly synced with DMarket.