you don't have to wait for coin mature to activate staking, when you start the wallet, when it finish loading and the chain is synced, wait at least another minute, then unlock it, and it will start staking, if you don't have mature coins at all, the diamond in the right low corner remains of the same color, until the first coins mature, then it change color, (become lighter) and at that moment the wallet try to stake on the network.

Coin mature time, if i remember well take one day after a previous stake.

Cheers