If your router is not issuing an IP address to your Apple Mac, you can try the following steps:

1. Restart Your Mac: Sometimes, simply restarting your computer can resolve the issue.

2. Restart Your Router: Unplug your router from the power source, wait for about 30 seconds, then plug it back in. Wait for all the lights to come back on before you try to reconnect.

3. Check Network Settings: Go to System Preferences > Network. Select the network connection you're having trouble with and click 'Advanced'. Click on the TCP/IP tab. If the IPv4 Address box doesn't show an IP address, click on the "Renew DHCP Lease" button.

4. Check Router Settings: Make sure your router is set to automatically assign IP addresses. This is usually an option in the router's settings, which you can access by typing the router's IP address into a web browser on a device that's connected to your network.

5. Disable and Enable Wi-Fi: Go to System Preferences > Network. Select Wi-Fi and turn it off. Wait for a few moments and then turn it back on.

6. Update Your Mac: Sometimes, software updates can fix network issues. Go to System Preferences > Software Update to check for updates.

7. Forget Network: Go to System Preferences > Network > Advanced. Here, you can see a list of networks your Mac has joined before. Select your network and click the minus (-) button to forget it. Then try reconnecting to the network.

8. Check for Interference: Other electronic devices can interfere with your Wi-Fi signal. Try moving your router away from these devices and see if that helps.

9. Contact Your ISP: If none of the above steps work, you may need to contact your Internet Service Provider. They can check if there's a problem with your connection and provide further assistance.

Remember, if you're not comfortable making these changes, it's always best to consult with a professional or your ISP.