There's just one primary reason why you cannot withdraw your earnings: you haven't yet hit the withdrawal threshold, in other words you have not earned the minimum amount of money applicable for withdrawal. New accounts default to 0.01BTC in A-ads, however the absolute minimum withdrawl amount is 0.0001 BTC or 10 000 satoshi. You cannot and should not request a withdrawal if you have less than that.
Our system makes withdrawals automatically every hour - if your withdrawal address is specified, no user intervention is required.
If you see that our system has already made a withdrawal, but your wallet hasn't received the money then you need to wait. The BTC network needs multiple confirmations for a transaction, and especially for little transactions it may take a significant amount of time, up to several hours.