We have seen issues on some, mostly bigger & complex, networks where Chrome OS & Chrome version 74 and newer are unable to see AirServer as a casting destination. 

We recommend trying the following to get AirServer to appear again:

1. In the address bar of the Chrome browser, go to chrome://flags/. 
2. Search for "Connect to cast devices on all IP addresses". 
3. Change the setting from "default" to "enabled".
4. Search for "Load Media Router Component Extension".
5. Change the setting from "default" to "enabled".