How to Open Firewall Ports
If you're using two PCs and you are having issues with Now Playing not working on your streaming computer then you might have a firewall blocking the connection.
You only need to follow these instructions once. After that Now Playing will continue to work.
Click on Start and type "firewall" and press enter
On the left, click on "Advanced Settings"
On the left, click on "Inbound Rules"
On the right side, click on "New Rule..."
Choose "Port" and then click "Next"
On your DJ computer look at the bottom of the app for your port number. The port number comes after "localhost". In this screenshot the port number is 9000.
Back to your streaming computer, select "Specific local ports" and type in your port number (like 9000), then click "Next".
On the next screen, click "Allow the connection" and click "Next".
On the next screen, you only want "Private" to have a checkmark. Domain and Public should not have a checkmark. Click "Next".
Next, name this rule "Now Playing" and click Finish. Now restart Now Playing on both computers.
Open System Preferences and click on "Security and Privacy"
Next click on the "Firewall" tab, then click on "Firewall Options..."
Scroll down and look for "Now Playing" and choose "Allow incoming connections".
Click on OK to save your changes then restart Now Playing on both computers.