The PowerServer 2021 (or later) license can only be an online license, therefore it requires persistent Internet connections when it is being used.
Make sure the machine where PowerServer Web APIs are running can connect with: https://apips.appeon.com, https://apipsoa.appeon.com, https://apips.appeon.net, https://apipsoa.appeon.net, https://apips2.appeon.com, and https://apips2.appeon.net.
Note
If the machine connects to Internet through a proxy server, make sure to configure the proxy server settings in the PowerServer Web APIs as well (ServerAPIs project > Server.json file > "ProxyOptions" block). The password for the proxy server, if any, must be an encrypted value (encrypted by the CustomizeDeploy.dll tool).
...
"ProxyOptions": {
"Server": "",
"Username": "",
"Password": ""
},
... 