Trade holds is a new feature that Steam recently added to the trading system in order to prevent your items from being stolen.
What it mean is that if your account doesn't have the necessary security options enabled, every trades that contains items from your inventory will be placed on hold for 3 days to give you time to react in case of an account hijack.
Obviously this affect the way betting works since waiting 3 days to receive items is not an option. This is why the bots will decline your deposit if the trade offer you are sending isn't protected by Steam Guard Mobile.
In order to bet on our website, you need to have the Steam Mobile Authenticator enabled on your account for at least 15 days as well as the trade confirmations turned on.
To do so, you can read the Steam FAQ about Trade Holds or follow the steps below:
From the mobile application: Steam Guard > Settings > Get Steam Guard codes on my phone
Once this is done, your Steam Guard status will change to "Protected by Steam Mobile AUthenticator"
Note that once Steam Guard Mobile is activated, you need to wait 15 days until the Trade hold restriction is removed.
Finaly, edit your profile to enable the trades confirmations: Edit Profile > My Privacy Settings > Confirmation of Trades
This step is mendatory and the confirmations needs to be enabled at all time.