Steam updated new Steam Guard Mobile Authenticator since December 10th of 2015. You can't deposit in our site if you don't meet the standard below.
You should open the Mobile Authenticator more than 7days and activate transaction confirmation function, otherwise, the website will show you this:
You can go here for instructions: http://www.vpgame.com/help/content.html?id=7771&lang=en_us
1.1 Go to "My VP", choose DOTA 2 Inventory or CS:GO Inventory according to the items you want to game.
1.2 Let's take DOTA 2 deposit for example to show you how to deposit items into your VP inventory.Go to "My VP", choose "DOTA2 Inventory", choose "Steam Inventory", and then choose an item(items),click the "Deposit" button.
1.3 Click to go to steam trade page.
1.4 Confirm and accept the offer.(The offer will run out of use in 10mins)
1.5 We now need to confirm in our mobile phone.
Withdraw items is much more like deposit items. Go to "My VP>CS:GO/DOTA2 Inventory> VP Inventory", then choose a item ,and click withdraw, choose a robot ,then wait the bot to give you an offer ,then take the offer.