Remembered Networks List |
It has to be on your list to remembered networks. In the System Preferences under Network you select your wireless connection (eg Wi-Fi) and then on the right side at the bottom click Advanced.
If your wireless network is already listed, use the minus button to remove it and then re-add it.
Make sure the box "Remember networks this computer has joined" is checked. In my screenshot it is the checkbox right under the plus sign.