When dealing with wireless technology, there are a number of circumstances that can block the signal. If the casting button does not appear, your computer does not show up on the list of destinations, or nothing appears on your computer after selecting it from the destination list, then your device is not able to communicate with AirServer for one of a few possible reasons.
The first thing you should try is powering off and restarting your device(s), computer(s), and router. Make sure your device and computer are on the same network.
If that does not solve your issue, run all available MacOS updates on your computer. Your device(s) should also be updated with the latest software updates.
Connection issues are most often caused by firewall software. You may have to adjust your firewall settings to allow AirServer to receive incoming networking traffic. Also ensure the same is done on any secondary firewalls your computer may have (like the built-in MacOS firewall - if enabled).
Another possible cause of your connection issue may be that your connection cannot handle the bandwidth required for streaming or mirroring. You can try connecting your computer to the network with an ethernet cable to see if the performance is better.
If you are still not able to connect, the issue may be with your router or network.
If your Wi-Fi router supports interface isolation or Wi-Fi isolation, make sure that these settings are turned off. These settings prevent wireless devices from communicating with each other. Refer to the documentation that came with your Wi-Fi router to access its settings and make sure your router has the latest firmware.
If you are behind a multi-subnet or Layer 3 network, as is common on larger networks and schools, please ensure that multi-casting is enabled and Bonjour is discoverable across the network. In most cases Bonjour will not be accessible across the network, as it's blocked by default, however, there is a guide you can look over or send to your networking Administrator to look over regarding Bonjour across Layer 3 Networks and Multiple Subnets.
For testing purposes, you could also try to download our AirServer Connect application from either the iOS App Store or Google Play Store. This application is a network helper tool that helps your phone discover AirServer on more complex networks.